diff --git a/conanfile.py b/conanfile.py
index 4cca3d28..b18a6524 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -46,7 +46,7 @@ class UnitsConan(ConanFile):
         "build_docs": [True, False]
     }
     default_options = {
-        "udls": True,
+        "udls": False,
         "downcast_mode": "on",
         "build_docs": True
     }
diff --git a/docs/usage.rst b/docs/usage.rst
index 37e6db6e..b8c1c951 100644
--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -128,7 +128,7 @@ udls
 
 **Values**: ``True``/``False``
 
-**Defaulted to**: ``True``
+**Defaulted to**: ``False``
 
 Determines if library should provide User Defined Literals (UDLs) for quantities of various units.
 
@@ -163,7 +163,7 @@ UNITS_UDLS
 
 **Values**: ``ON``/``OFF``
 
-**Defaulted to**: ``ON``
+**Defaulted to**: ``OFF``
 
 Equivalent to `udls`_.
 
diff --git a/example/alternative_namespaces/CMakeLists.txt b/example/alternative_namespaces/CMakeLists.txt
index 139c9d94..1095d79f 100644
--- a/example/alternative_namespaces/CMakeLists.txt
+++ b/example/alternative_namespaces/CMakeLists.txt
@@ -25,6 +25,7 @@ cmake_minimum_required(VERSION 3.2)
 function(add_example target)
     add_executable(${target}_alt ${target}.cpp)
     target_link_libraries(${target}_alt PRIVATE mp-units::mp-units)
+    target_compile_definitions(${target}_alt PRIVATE UNITS_UDLS=1)
 endfunction()
 
 add_example(box_example mp-units::si)
diff --git a/example/avg_speed.cpp b/example/avg_speed.cpp
index e00d90d7..4b03a180 100644
--- a/example/avg_speed.cpp
+++ b/example/avg_speed.cpp
@@ -73,8 +73,8 @@ void example()
 {
   // SI (int)
   {
-    using namespace units::isq::si::literals;
-    constexpr Length auto distance = 220_q_km;     // constructed from a UDL
+    using namespace units::isq::si::references;
+    constexpr Length auto distance = 220 * km;     // constructed from a reference
     constexpr si::time<si::hour, int> duration(2); // constructed from a value
 
     std::cout << "SI units with 'int' as representation\n";
@@ -87,8 +87,8 @@ void example()
 
   // SI (double)
   {
-    using namespace units::isq::si::literals;
-    constexpr Length auto distance = 220._q_km; // constructed from a UDL
+    using namespace units::isq::si::references;
+    constexpr Length auto distance = 220. * km; // constructed from a reference
     constexpr si::time<si::hour> duration(2);   // constructed from a value
 
     std::cout << "\nSI units with 'double' as representation\n";
@@ -103,8 +103,8 @@ void example()
 
   // Customary Units (int)
   {
-    using namespace units::isq::si::international::literals;
-    constexpr Length auto distance = 140_q_mi;     // constructed from a UDL
+    using namespace units::isq::si::international::references;
+    constexpr Length auto distance = 140 * mi;     // constructed from a reference
     constexpr si::time<si::hour, int> duration(2); // constructed from a value
 
     std::cout << "\nUS Customary Units with 'int' as representation\n";
@@ -119,8 +119,8 @@ void example()
 
   // Customary Units (double)
   {
-    using namespace units::isq::si::international::literals;
-    constexpr Length auto distance = 140._q_mi; // constructed from a UDL
+    using namespace units::isq::si::international::references;
+    constexpr Length auto distance = 140. * mi; // constructed from a reference
     constexpr si::time<si::hour> duration(2);   // constructed from a value
 
     std::cout << "\nUS Customary Units with 'double' as representation\n";
@@ -137,8 +137,8 @@ void example()
 
   // CGS (int)
   {
-    using namespace units::isq::si::cgs::literals;
-    constexpr Length auto distance = 22'000'000_q_cm; // constructed from a UDL
+    using namespace units::isq::si::cgs::references;
+    constexpr Length auto distance = 22'000'000 * cm;     // constructed from a reference
     constexpr si::cgs::time<si::hour, int> duration(2);   // constructed from a value
 
     std::cout << "\nCGS units with 'int' as representation\n";
@@ -156,8 +156,8 @@ void example()
 
   // CGS (double)
   {
-    using namespace units::isq::si::cgs::literals;
-    constexpr Length auto distance = 22'000'000._q_cm; // constructed from a UDL
+    using namespace units::isq::si::cgs::references;
+    constexpr Length auto distance = 22'000'000. * cm; // constructed from a reference
     constexpr si::cgs::time<si::hour> duration(2);     // constructed from a value
 
     std::cout << "\nCGS units with 'double' as representation\n";
diff --git a/example/box_example.cpp b/example/box_example.cpp
index 0e7afbaf..92743e3e 100644
--- a/example/box_example.cpp
+++ b/example/box_example.cpp
@@ -39,43 +39,37 @@
 namespace {
 
 using namespace units::isq;
+using namespace si::references;
 
-using m = si::metre;
-using m2 = si::square_metre;
-using m3 = si::cubic_metre;
-using kg = si::kilogram;
-using N = si::newton;
-using kgpm3 = si::kilogram_per_metre_cub;
-
-inline constexpr auto g = si::si2019::standard_gravity<>;
-inline constexpr si::density<kgpm3> air_density(1.225);
+inline constexpr Acceleration auto g = si::si2019::standard_gravity<>;
+inline constexpr Density auto air_density = 1.225 * (kg / m3);
 
 
 class Box {
-  si::area<m2> base_;
-  si::length<m> height_;
-  si::density<kgpm3> density_ = air_density;
+  si::area<si::square_metre> base_;
+  si::length<si::metre> height_;
+  si::density<si::kilogram_per_metre_cub> density_ = air_density;
 public:
-  constexpr Box(const si::length<m>& length, const si::length<m>& width, si::length<m> height) : base_(length * width), height_(std::move(height)) {}
+  constexpr Box(const si::length<si::metre>& length, const si::length<si::metre>& width, si::length<si::metre> height) : base_(length * width), height_(std::move(height)) {}
 
-  [[nodiscard]] constexpr si::force<N> filled_weight() const
+  [[nodiscard]] constexpr si::force<si::newton> filled_weight() const
   {
-    const si::volume<m3> volume = base_ * height_;
-    const si::mass<kg> mass = density_ * volume;
+    const Volume auto volume = base_ * height_;
+    const Mass auto mass = density_ * volume;
     return mass * g;
   }
 
-  [[nodiscard]] constexpr si::length<m> fill_level(const si::mass<kg>& measured_mass) const
+  [[nodiscard]] constexpr si::length<si::metre> fill_level(const si::mass<si::kilogram>& measured_mass) const
   {
     return height_ * measured_mass * g / filled_weight();
   }
 
-  [[nodiscard]] constexpr si::volume<m3> spare_capacity(const si::mass<kg>& measured_mass) const
+  [[nodiscard]] constexpr si::volume<si::cubic_metre> spare_capacity(const si::mass<si::kilogram>& measured_mass) const
   {
     return (height_ - fill_level(measured_mass)) * base_;
   }
 
-  constexpr void set_contents_density(const si::density<kgpm3>& density_in)
+  constexpr void set_contents_density(const si::density<si::kilogram_per_metre_cub>& density_in)
   {
     assert(density_in > air_density);
     density_ = density_in;
@@ -88,14 +82,13 @@ public:
 int main()
 {
   using namespace units;
-  using namespace si::literals;
 
-  const si::length<m> height(200.0_q_mm);
-  auto box = Box(1000.0_q_mm, 500.0_q_mm, height);
-  box.set_contents_density(1000.0_q_kg_per_m3);
+  const si::length<si::metre> height = 200.0 * mm;
+  auto box = Box(1000.0 * mm, 500.0 * mm, height);
+  box.set_contents_density(1000.0 * (kg / m3));
 
-  const auto fill_time = 200.0_q_s;        // time since starting fill
-  const auto measured_mass = 20.0_q_kg;    // measured mass at fill_time
+  const auto fill_time = 200.0 * s;        // time since starting fill
+  const auto measured_mass = 20.0 * kg;    // measured mass at fill_time
 
   const Length auto fill_level = box.fill_level(measured_mass);
   const Dimensionless auto fill_percent = quantity_cast<percent>(fill_level / height);
diff --git a/example/capacitor_time_curve.cpp b/example/capacitor_time_curve.cpp
index e1300e91..5d41e054 100644
--- a/example/capacitor_time_curve.cpp
+++ b/example/capacitor_time_curve.cpp
@@ -34,27 +34,28 @@ int main()
 {
   using namespace units::isq;
   using namespace units::isq::si;
+  using namespace units::isq::si::references;
 
   std::cout << "mp-units capacitor time curve example...\n";
   std::cout.setf(std::ios_base::fixed, std::ios_base::floatfield);
   std::cout.precision(3);
 
-  constexpr auto C = 0.47_q_uF;
-  constexpr auto V0 = 5.0_q_V;
-  constexpr auto R = 4.7_q_kR;
+  constexpr auto C = 0.47 * uF;
+  constexpr auto V0 = 5.0 * V;
+  constexpr auto R = 4.7 * kR;
 
-  for (auto t = 0_q_ms; t <= 50_q_ms; ++t) {
+  for (auto t = 0 * ms; t <= 50 * ms; ++t) {
     const Voltage auto Vt = V0 * units::exp(-t / (R * C));
 
     std::cout << "at " << t << " voltage is ";
 
-    if (Vt >= 1_q_V)
+    if (Vt >= 1 * V)
       std::cout << Vt;
-    else if (Vt >= 1_q_mV)
+    else if (Vt >= 1 * mV)
       std::cout << quantity_cast<millivolt>(Vt);
-    else if (Vt >= 1_q_uV)
+    else if (Vt >= 1 * uV)
       std::cout << quantity_cast<microvolt>(Vt);
-    else if (Vt >= 1_q_nV)
+    else if (Vt >= 1 * nV)
       std::cout << quantity_cast<nanovolt>(Vt);
     else
       std::cout << quantity_cast<picovolt>(Vt);
diff --git a/example/clcpp_response.cpp b/example/clcpp_response.cpp
index 6a130b2f..2d3516d3 100644
--- a/example/clcpp_response.cpp
+++ b/example/clcpp_response.cpp
@@ -29,55 +29,54 @@
 
 namespace {
 
-using namespace units;
-
 void simple_quantities()
 {
-  using namespace units::isq::si;
-  using namespace units::isq::si::international;
+  using namespace units::isq;
+  using namespace units::isq::si::references;
+  using namespace units::isq::si::international::references;
 
-  using distance = length<metre>;
-  using duration = isq::si::time<second>;
+  using distance = si::length<si::metre>;
+  using duration = si::time<si::second>;
 
-  constexpr distance km = 1.0_q_km;
-  constexpr distance miles = 1.0_q_mi;
+  constexpr distance kilometers = 1.0 * km;
+  constexpr distance miles = 1.0 * mi;
 
-  constexpr duration sec = 1_q_s;
-  constexpr duration min = 1_q_min;
-  constexpr duration hr = 1_q_h;
+  constexpr duration seconds = 1 * s;
+  constexpr duration minutes = 1 * min;
+  constexpr duration hours = 1 * h;
 
   std::cout << "A physical quantities library can choose the simple\n";
   std::cout << "option to provide output using a single type for each base unit:\n\n";
-  std::cout << km << '\n';
+  std::cout << kilometers << '\n';
   std::cout << miles << '\n';
-  std::cout << sec << '\n';
-  std::cout << min << '\n';
-  std::cout << hr << "\n\n";
+  std::cout << seconds << '\n';
+  std::cout << minutes << '\n';
+  std::cout << hours << "\n\n";
 }
 
 void quantities_with_typed_units()
 {
   using namespace units::isq;
-  using namespace units::isq::si;
-  using namespace units::isq::si::international;
+  using namespace units::isq::si::references;
+  using namespace units::isq::si::international::references;
 
-  constexpr length<kilometre> km = 1.0_q_km;
-  constexpr length<mile> miles = 1.0_q_mi;
+  constexpr si::length<si::kilometre> kilometers = 1.0 * km;
+  constexpr si::length<si::international::mile> miles = 1.0 * mi;
 
   std::cout.precision(6);
 
-  constexpr si::time<second> sec = 1_q_s;
-  constexpr si::time<minute> min = 1_q_min;
-  constexpr si::time<hour> hr = 1_q_h;
+  constexpr si::time<si::second> seconds = 1 * s;
+  constexpr si::time<si::minute> minutes = 1 * min;
+  constexpr si::time<si::hour> hours = 1 * h;
 
   std::cout << "A more flexible option is to provide separate types for each unit,\n\n";
-  std::cout << km << '\n';
+  std::cout << kilometers << '\n';
   std::cout << miles << '\n';
-  std::cout << sec << '\n';
-  std::cout << min << '\n';
-  std::cout << hr << "\n\n";
+  std::cout << seconds << '\n';
+  std::cout << minutes << '\n';
+  std::cout << hours << "\n\n";
 
-  constexpr length<metre> meter = 1_q_m;
+  constexpr si::length<si::metre> meter = 1 * m;
   std::cout << "then a wide range of pre-defined units can be defined and converted,\n"
                " for consistency and repeatability across applications:\n\n";
 
@@ -105,34 +104,35 @@ void quantities_with_typed_units()
 
 void calcs_comparison()
 {
-  using namespace units::isq::si;
+  using namespace units::isq;
+  using namespace units::isq::si::references;
 
   std::cout << "\nA distinct unit for each type is efficient and accurate\n"
                "when adding two values of the same very big\n"
                "or very small type:\n\n";
 
-  length<femtometre, float> L1A = 2._q_fm;
-  length<femtometre, float> L2A = 3._q_fm;
-  length<femtometre, float> LrA = L1A + L2A;
+  si::length<si::femtometre, float> L1A = 2. * fm;
+  si::length<si::femtometre, float> L2A = 3. * fm;
+  si::length<si::femtometre, float> LrA = L1A + L2A;
   fmt::print("{:%.30Q %q}\n + {:%.30Q %q}\n   = {:%.30Q %q}\n\n", L1A, L2A, LrA);
 
   std::cout << "The single unit method must convert large\n"
                "or small values in other units to the base unit.\n"
                "This is both inefficient and inaccurate\n\n";
 
-  length<metre, float> L1B = L1A;
-  length<metre, float> L2B = L2A;
-  length<metre, float> LrB = L1B + L2B;
+  si::length<si::metre, float> L1B = L1A;
+  si::length<si::metre, float> L2B = L2A;
+  si::length<si::metre, float> LrB = L1B + L2B;
   fmt::print("{:%.30Q %q}\n + {:%.30Q %q}\n   = {:%.30Q %q}\n\n", L1B, L2B, LrB);
 
   std::cout << "In multiplication and division:\n\n";
 
-  area<square_femtometre, float> ArA = L1A * L2A;
+  si::area<si::square_femtometre, float> ArA = L1A * L2A;
   fmt::print("{:%.30Q %q}\n * {:%.30Q %q}\n   = {:%.30Q %q}\n\n", L1A, L2A, ArA);
 
   std::cout << "similar problems arise\n\n";
 
-  area<square_metre, float> ArB = L1B * L2B;
+  si::area<si::square_metre, float> ArB = L1B * L2B;
   fmt::print("{:%.30Q %q}\n * {:%.30Q %q}\n   = {:%.30Q %q}\n\n", L1B, L2B, ArB);
 }
 
diff --git a/example/conversion_factor.cpp b/example/conversion_factor.cpp
index 7e370522..436242ec 100644
--- a/example/conversion_factor.cpp
+++ b/example/conversion_factor.cpp
@@ -43,10 +43,11 @@ inline constexpr std::common_type_t<typename Target::rep, typename Source::rep>
 int main()
 {
   using namespace units::isq::si;
+  using namespace units::isq::si::references;
 
   std::cout << "conversion factor in mp-units...\n\n";
 
-  constexpr length<metre> lengthA = 2.0_q_m;
+  constexpr length<metre> lengthA = 2.0 * m;
   constexpr length<millimetre> lengthB = lengthA;
 
   std::cout << fmt::format("lengthA( {} ) and lengthB( {} )\n", lengthA, lengthB)
diff --git a/example/foot_pound_second.cpp b/example/foot_pound_second.cpp
index 841068f7..0fafd1dc 100644
--- a/example/foot_pound_second.cpp
+++ b/example/foot_pound_second.cpp
@@ -26,6 +26,7 @@
 #include <units/isq/si/fps/mass.h>
 #include <units/isq/si/fps/power.h>
 #include <units/isq/si/fps/speed.h>
+#include <units/isq/si/fps/volume.h>
 #include <units/isq/si/length.h>
 #include <units/isq/si/mass.h>
 #include <units/isq/si/power.h>
@@ -62,8 +63,8 @@ auto fmt_line(const Q a)
 // Print the ship details in the units as defined in the Ship struct, in other si::imperial units, and in SI
 void print_details(std::string_view description, const Ship& ship)
 {
-  using namespace units::isq::si::fps::literals;
-  const auto waterDensity = 62.4_q_lb_per_ft3;
+  using namespace units::isq::si::fps::references;
+  const auto waterDensity = 62.4 * (lb / ft3);
   std::cout << fmt::format("{}\n", description);
   std::cout << fmt::format("{:20} : {}\n", "length",    fmt_line<si::fps::length<si::fps::yard>, si::length<si::metre>>(ship.length))
             << fmt::format("{:20} : {}\n", "draft",     fmt_line<si::fps::length<si::fps::yard>, si::length<si::metre>>(ship.draft))
@@ -79,17 +80,18 @@ void print_details(std::string_view description, const Ship& ship)
 
 int main()
 {
-  using namespace units::isq::si::literals;
-  using namespace units::isq::si::fps::literals;
+  using namespace units::isq::si::references;
+  using namespace units::isq::si::fps::references;
+  using units::isq::si::fps::references::ft;  // collides with si::femtotonne (alias unit of mass)
   
   // KMS Bismark, using the units the Germans would use, taken from Wiki
-  auto bismark = Ship{.length{251._q_m}, .draft{9.3_q_m}, .beam{36_q_m}, .speed{56_q_km_per_h}, .mass{50'300_q_t}, .mainGuns{380_q_mm}, .shellMass{800_q_kg}, .shellSpeed{820._q_m_per_s}, .power{110.45_q_kW}};
+  auto bismark = Ship{.length{251. * m}, .draft{9.3 * m}, .beam{36 * m}, .speed{56 * (km / h)}, .mass{50'300 * t}, .mainGuns{380 * mm}, .shellMass{800 * kg}, .shellSpeed{820. * (m / s)}, .power{110.45 * kW}};
 
   // USS Iowa, using units from the foot-pound-second system
-  auto iowa = Ship{.length{860._q_ft}, .draft{37._q_ft + 2._q_in}, .beam{108._q_ft + 2._q_in}, .speed{33_q_knot}, .mass{57'540_q_lton}, .mainGuns{16_q_in}, .shellMass{2700_q_lb}, .shellSpeed{2690._q_ft_per_s}, .power{212'000_q_hp}};
+  auto iowa = Ship{.length{860. * ft}, .draft{37. * ft + 2. * in}, .beam{108. * ft + 2. * in}, .speed{33 * knot}, .mass{57'540 * lton}, .mainGuns{16 * in}, .shellMass{2700 * lb}, .shellSpeed{2690. * (ft / s)}, .power{212'000 * hp}};
 
   // HMS King George V, using units from the foot-pound-second system
-  auto kgv = Ship{.length{745.1_q_ft}, .draft{33._q_ft + 7.5_q_in}, .beam{103.2_q_ft + 2.5_q_in}, .speed{28.3_q_knot}, .mass{42'245_q_lton}, .mainGuns{14_q_in}, .shellMass{1'590_q_lb}, .shellSpeed{2483._q_ft_per_s}, .power{110'000_q_hp}};
+  auto kgv = Ship{.length{745.1 * ft}, .draft{33. * ft + 7.5 * in}, .beam{103.2 * ft + 2.5 * in}, .speed{28.3 * knot}, .mass{42'245 * lton}, .mainGuns{14 * in}, .shellMass{1'590 * lb}, .shellSpeed{2483. * (ft / s)}, .power{110'000 * hp}};
 
   print_details("KMS Bismark, defined in appropriate units from the SI system", bismark);
   std::cout << "\n\n";
diff --git a/example/hello_units.cpp b/example/hello_units.cpp
index b7513dbd..6208cec2 100644
--- a/example/hello_units.cpp
+++ b/example/hello_units.cpp
@@ -20,6 +20,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#define UNITS_UDLS 1
+
 #include <units/format.h>
 #include <units/isq/si/international/length.h>
 #include <units/isq/si/international/speed.h> // IWYU pragma: keep
diff --git a/example/kalman_filter-alpha_beta_filter_example2.cpp b/example/kalman_filter-alpha_beta_filter_example2.cpp
index 52f53ead..68f0fdf0 100644
--- a/example/kalman_filter-alpha_beta_filter_example2.cpp
+++ b/example/kalman_filter-alpha_beta_filter_example2.cpp
@@ -41,9 +41,9 @@ struct state_variable {
 };
 
 using namespace units::isq;
-using namespace units::isq::si::literals;
+using namespace units::isq::si::references;
 
-constexpr auto radar_transmit_interval = 5.0_q_s;
+constexpr auto radar_transmit_interval = 5.0 * s;
 constexpr double kalman_range_gain = 0.2;
 constexpr double kalman_speed_gain = 0.1;
 
@@ -74,16 +74,16 @@ int main()
   std::cout << "\n\n1d aircraft α-β filter example2 from https://www.kalmanfilter.net/alphabeta.html#ex2";
   std::cout << "\n\n";
 
-  constexpr auto measurements = std::array{0.0_q_m,  // N.B measurement[0] is unknown and unused
-                                           30110.0_q_m, 30265.0_q_m, 30740.0_q_m, 30750.0_q_m, 31135.0_q_m,
-                                           31015.0_q_m, 31180.0_q_m, 31610.0_q_m, 31960.0_q_m, 31865.0_q_m};
+  constexpr auto measurements = std::array{0.0 * m,  // N.B measurement[0] is unknown and unused
+                                           30110.0 * m, 30265.0 * m, 30740.0 * m, 30750.0 * m, 31135.0 * m,
+                                           31015.0 * m, 31180.0 * m, 31610.0 * m, 31960.0 * m, 31865.0 * m};
 
   constexpr auto num_measurements = measurements.size();
 
   std::array<state, num_measurements> track;
   // We need an initial estimate of track[0] as there is no previous state to get a prediction from
-  track[0].range.estimated_current_state = 30'000_q_m;
-  track[0].speed.estimated_current_state = 40.0_q_m_per_s;
+  track[0].range.estimated_current_state = 30'000 * m;
+  track[0].speed.estimated_current_state = 40.0 * (m / s);
 
   for (auto n = 0U; n < num_measurements; ++n) {
     if (n > 0) {
diff --git a/example/linear_algebra.cpp b/example/linear_algebra.cpp
index e98b69bd..1dbd658c 100644
--- a/example/linear_algebra.cpp
+++ b/example/linear_algebra.cpp
@@ -60,7 +60,7 @@ std::ostream& operator<<(std::ostream& os, const matrix<ET, OT>& v)
 namespace {
 
 using namespace units::isq;
-using namespace units::isq::si::literals;
+using namespace units::isq::si::references;
 
 template<typename Rep = double>
 using vector = std::math::fs_vector<Rep, 3>;
@@ -73,9 +73,9 @@ void vector_of_quantity_add()
 {
   std::cout << "\nvector_of_quantity_add:\n";
 
-  vector<si::length<si::metre>> v = { 1_q_m, 2_q_m, 3_q_m };
-  vector<si::length<si::metre>> u = { 3_q_m, 2_q_m, 1_q_m };
-  vector<si::length<si::kilometre>> t = { 3_q_km, 2_q_km, 1_q_km };
+  vector<si::length<si::metre>> v = { 1 * m, 2 * m, 3 * m };
+  vector<si::length<si::metre>> u = { 3 * m, 2 * m, 1 * m };
+  vector<si::length<si::kilometre>> t = { 3 * km, 2 * km, 1 * km };
 
   std::cout << "v = " << v << "\n";
   std::cout << "u = " << u << "\n";
@@ -90,28 +90,28 @@ void vector_of_quantity_multiply_same()
 {
   std::cout << "\nvector_of_quantity_multiply_same:\n";
 
-  vector<si::length<si::metre>> v = { 1_q_m, 2_q_m, 3_q_m };
-  vector<si::length<si::metre>> u = { 3_q_m, 2_q_m, 1_q_m };
+  vector<si::length<si::metre>> v = { 1 * m, 2 * m, 3 * m };
+  vector<si::length<si::metre>> u = { 3 * m, 2 * m, 1 * m };
 
   std::cout << "v = " << v << "\n";
   std::cout << "u = " << u << "\n";
 
   std::cout << "v * u    = " << v * u << "\n";
-  std::cout << "2_q_m * v = " << 2._q_m * v << "\n";
+  std::cout << "2 * m * v = " << 2. * m * v << "\n";
 }
 
 void vector_of_quantity_multiply_different()
 {
   std::cout << "\nvector_of_quantity_multiply_different:\n";
 
-  vector<si::force<si::newton>> v = { 1_q_N, 2_q_N, 3_q_N };
-  vector<si::length<si::metre>> u = { 3_q_m, 2_q_m, 1_q_m };
+  vector<si::force<si::newton>> v = { 1 * N, 2 * N, 3 * N };
+  vector<si::length<si::metre>> u = { 3 * m, 2 * m, 1 * m };
 
   std::cout << "v = " << v << "\n";
   std::cout << "u = " << u << "\n";
 
   std::cout << "v * u    = " << v * u << "\n";
-  std::cout << "2_q_N * u = " << 2._q_N * u << "\n";
+  std::cout << "2 * N * u = " << 2. * N * u << "\n";
   std::cout << "2 * u    = " << 2 * u << "\n";
 }
 
@@ -119,12 +119,12 @@ void vector_of_quantity_divide_by_scalar()
 {
   std::cout << "\nvector_of_quantity_divide_by_scalar:\n";
 
-  vector<si::length<si::metre>> v = { 4_q_m, 8_q_m, 12_q_m };
+  vector<si::length<si::metre>> v = { 4 * m, 8 * m, 12 * m };
 
   std::cout << "v = " << v << "\n";
 
   // TODO Uncomment when bug in the LA is fixed
-  // std::cout << "v / 2_q_s = " << v / 2_q_s << "\n";
+  // std::cout << "v / (2 * s) = " << v / (2 * s) << "\n";
   // std::cout << "v / 2 = " << v / 2 << "\n";
 }
 
@@ -140,9 +140,9 @@ void matrix_of_quantity_add()
 {
   std::cout << "\nmatrix_of_quantity_add:\n";
 
-  matrix<si::length<si::metre>> v = {{ 1_q_m, 2_q_m, 3_q_m }, { 4_q_m, 5_q_m, 6_q_m }, { 7_q_m, 8_q_m, 9_q_m }};
-  matrix<si::length<si::metre>> u = {{ 3_q_m, 2_q_m, 1_q_m }, { 3_q_m, 2_q_m, 1_q_m }, { 3_q_m, 2_q_m, 1_q_m }};
-  matrix<si::length<si::millimetre>> t = {{ 3_q_mm, 2_q_mm, 1_q_mm }, { 3_q_mm, 2_q_mm, 1_q_mm }, { 3_q_mm, 2_q_mm, 1_q_mm }};
+  matrix<si::length<si::metre>> v = {{ 1 * m, 2 * m, 3 * m }, { 4 * m, 5 * m, 6 * m }, { 7 * m, 8 * m, 9 * m }};
+  matrix<si::length<si::metre>> u = {{ 3 * m, 2 * m, 1 * m }, { 3 * m, 2 * m, 1 * m }, { 3 * m, 2 * m, 1 * m }};
+  matrix<si::length<si::millimetre>> t = {{ 3 * mm, 2 * mm, 1 * mm }, { 3 * mm, 2 * mm, 1 * mm }, { 3 * mm, 2 * mm, 1 * mm }};
 
   std::cout << "v =\n" << v << "\n";
   std::cout << "u =\n" << u << "\n";
@@ -159,28 +159,28 @@ void matrix_of_quantity_multiply_same()
 {
   std::cout << "\nmatrix_of_quantity_multiply_same:\n";
   
-  matrix<si::length<si::metre>> v = {{ 1_q_m, 2_q_m, 3_q_m }, { 4_q_m, 5_q_m, 6_q_m }, { 7_q_m, 8_q_m, 9_q_m }};
-  vector<si::length<si::metre>> u = { 3_q_m, 2_q_m, 1_q_m };
+  matrix<si::length<si::metre>> v = {{ 1 * m, 2 * m, 3 * m }, { 4 * m, 5 * m, 6 * m }, { 7 * m, 8 * m, 9 * m }};
+  vector<si::length<si::metre>> u = { 3 * m, 2 * m, 1 * m };
 
   std::cout << "v =\n" << v << "\n";
   std::cout << "u =\n" << u << "\n";
 
   std::cout << "v * u =\n" << v * u << "\n";
-  std::cout << "2_q_m * u =\n" << 2._q_m * u << "\n";
+  std::cout << "2 * m * u =\n" << 2. * m * u << "\n";
 }
 
 void matrix_of_quantity_multiply_different()
 {
   std::cout << "\nmatrix_of_quantity_multiply_different:\n";
 
-  vector<si::force<si::newton>> v = { 1_q_N, 2_q_N, 3_q_N };
-  matrix<si::length<si::metre>> u = {{ 1_q_m, 2_q_m, 3_q_m }, { 4_q_m, 5_q_m, 6_q_m }, { 7_q_m, 8_q_m, 9_q_m }};
+  vector<si::force<si::newton>> v = { 1 * N, 2 * N, 3 * N };
+  matrix<si::length<si::metre>> u = {{ 1 * m, 2 * m, 3 * m }, { 4 * m, 5 * m, 6 * m }, { 7 * m, 8 * m, 9 * m }};
 
   std::cout << "v =\n" << v << "\n";
   std::cout << "u =\n" << u << "\n";
 
   std::cout << "v * u =\n" << v * u << "\n";
-  std::cout << "2_q_N * u =\n" << 2._q_N * u << "\n";
+  std::cout << "2 * N * u =\n" << 2. * N * u << "\n";
   std::cout << "2 * u =\n" << 2 * u << "\n";
 }
 
@@ -188,12 +188,12 @@ void matrix_of_quantity_divide_by_scalar()
 {
   std::cout << "\nmatrix_of_quantity_divide_by_scalar:\n";
 
-  matrix<si::length<si::metre>> v = {{ 2_q_m, 4_q_m, 6_q_m }, { 4_q_m, 6_q_m, 8_q_m }, { 8_q_m, 4_q_m, 2_q_m }};
+  matrix<si::length<si::metre>> v = {{ 2 * m, 4 * m, 6 * m }, { 4 * m, 6 * m, 8 * m }, { 8 * m, 4 * m, 2 * m }};
 
   std::cout << "v =\n" << v << "\n";
 
   // TODO Uncomment when bug in the LA is fixed
-  // std::cout << "v / 2_q_s =\n" << v / 2_q_s << "\n";
+  // std::cout << "v / (2 * s) =\n" << v / (2 * s) << "\n";
   // std::cout << "v / 2 =\n" << v / 2 << "\n";
 }
 
@@ -239,7 +239,7 @@ void quantity_of_vector_multiply_same()
   std::cout << "u = " << u << "\n";
 
   std::cout << "v * u    = " << v * u << "\n";
-  std::cout << "2_q_m * v = " << 2._q_m * v << "\n";
+  std::cout << "2 * m * v = " << 2. * m * v << "\n";
 }
 
 void quantity_of_vector_multiply_different()
@@ -253,7 +253,7 @@ void quantity_of_vector_multiply_different()
   std::cout << "u = " << u << "\n";
 
   std::cout << "v * u    = " << v * u << "\n";
-  std::cout << "2_q_N * u = " << 2._q_N * u << "\n";
+  std::cout << "2 * N * u = " << 2. * N * u << "\n";
   std::cout << "2 * u    = " << 2 * u << "\n";
 }
 
@@ -266,7 +266,7 @@ void quantity_of_vector_divide_by_scalar()
   std::cout << "v = " << v << "\n";
 
   // TODO Uncomment when bug in the LA is fixed
-  // std::cout << "v / 2_q_s = " << v / 2_q_s << "\n";
+  // std::cout << "v / 2 * s = " << v / 2 * s << "\n";
   // std::cout << "v / 2 = " << v / 2 << "\n";
 }
 
@@ -311,7 +311,7 @@ void quantity_of_matrix_multiply_same()
   std::cout << "u =\n" << u << "\n";
 
   std::cout << "v * u =\n" << v * u << "\n";
-  std::cout << "2_q_m * u =\n" << 2._q_m * u << "\n";
+  std::cout << "2 * m * u =\n" << 2. * m * u << "\n";
 }
 
 void quantity_of_matrix_multiply_different()
@@ -325,7 +325,7 @@ void quantity_of_matrix_multiply_different()
   std::cout << "u =\n" << u << "\n";
 
   std::cout << "v * u =\n" << v * u << "\n";
-  std::cout << "2_q_N * u =\n" << 2._q_N * u << "\n";
+  std::cout << "2 * N * u =\n" << 2. * N * u << "\n";
   std::cout << "2 * u =\n" << 2 * u << "\n";
 }
 
@@ -338,7 +338,7 @@ void quantity_of_matrix_divide_by_scalar()
   std::cout << "v =\n" << v << "\n";
 
   // TODO Uncomment when bug in the LA is fixed
-  // std::cout << "v / 2_q_s =\n" << v / 2_q_s << "\n";
+  // std::cout << "v / (2 * s) =\n" << v / (2 * s) << "\n";
   // std::cout << "v / 2 =\n" << v / 2 << "\n";
 }
 
diff --git a/example/total_energy.cpp b/example/total_energy.cpp
index 7420f241..0398c82f 100644
--- a/example/total_energy.cpp
+++ b/example/total_energy.cpp
@@ -43,14 +43,14 @@ Energy auto total_energy(Momentum auto p, Mass auto m, Speed auto c)
 void si_example()
 {
   using namespace units::isq::si;
-  using GeV = gigaelectronvolt;
+  using namespace units::isq::si::references;
 
   constexpr Speed auto c = si2019::speed_of_light<>;
 
   std::cout << "\n*** SI units (c = " << c << ") ***\n";
 
-  const Momentum auto p = 4._q_GeV / c;
-  const Mass auto m = 3._q_GeV / pow<2>(c);
+  const Momentum auto p = 4. * GeV / c;
+  const Mass auto m = 3. * GeV / pow<2>(c);
   const Energy auto E = total_energy(p, m, c);
 
   std::cout << "[in GeV]\n"
@@ -68,17 +68,16 @@ void si_example()
             << "E = " << E_si << "\n";
 
   std::cout << "\n[converted from SI units back to GeV]\n"
-            << "E = " << quantity_cast<GeV>(E_si) << "\n";
+            << "E = " << quantity_cast<gigaelectronvolt>(E_si) << "\n";
 }
 
 void natural_example()
 {
   using namespace units::isq::natural;
-  using GeV = gigaelectronvolt;
 
   constexpr Speed auto c = speed_of_light<>;
-  const momentum<GeV> p(4);
-  const mass<GeV> m(3);
+  const momentum<gigaelectronvolt> p(4);
+  const mass<gigaelectronvolt> m(3);
   const Energy auto E = total_energy(p, m, c);
 
   std::cout << "\n*** Natural units (c = " << c << ") ***\n"
diff --git a/example/unknown_dimension.cpp b/example/unknown_dimension.cpp
index aed204d8..8e5fe29a 100644
--- a/example/unknown_dimension.cpp
+++ b/example/unknown_dimension.cpp
@@ -38,15 +38,15 @@ constexpr units::isq::Speed auto avg_speed(D d, T t)
 void example()
 {
   using namespace units::isq;
-  using namespace units::isq::si::literals;
+  using namespace units::isq::si::references;
 
-  Length auto d1 = 123_q_m;
-  Time auto t1 = 10_q_s;
+  Length auto d1 = 123 * m;
+  Time auto t1 = 10 * s;
   Speed auto v1 = avg_speed(d1, t1);
 
-  auto temp1 = v1 * 50_q_m;  // produces intermediate unknown dimension with 'unknown_coherent_unit' as its 'coherent_unit'
-  Speed auto v2 = temp1 / 100_q_m; // back to known dimensions again
-  Length auto d2 = v2 * 60_q_s;
+  auto temp1 = v1 * (50 * m);  // produces intermediate unknown dimension with 'unknown_coherent_unit' as its 'coherent_unit'
+  Speed auto v2 = temp1 / (100 * m); // back to known dimensions again
+  Length auto d2 = v2 * (60 * s);
 
   std::cout << "d1 = " << d1 << '\n';
   std::cout << "t1 = " << t1 << '\n';
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e6f79c03..2707c44d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -27,7 +27,7 @@ project(mp-units
 )
 
 option(UNITS_AS_SYSTEM_HEADERS "Exports library as system headers" OFF)
-option(UNITS_UDLS "Enables definitions of User Defined Literals (UDLs) provided for quantities of various units" ON)
+option(UNITS_UDLS "Enables definitions of User Defined Literals (UDLs) provided for quantities of various units" OFF)
 
 message(STATUS "UNITS_AS_SYSTEM_HEADERS: ${UNITS_AS_SYSTEM_HEADERS}")
 message(STATUS "UNITS_UDLS: ${UNITS_UDLS}")
diff --git a/test/unit_test/runtime/CMakeLists.txt b/test/unit_test/runtime/CMakeLists.txt
index 08bace2f..e70c8cc3 100644
--- a/test/unit_test/runtime/CMakeLists.txt
+++ b/test/unit_test/runtime/CMakeLists.txt
@@ -35,6 +35,7 @@ target_link_libraries(unit_tests_runtime PRIVATE
     mp-units::mp-units
     Catch2::Catch2
 )
+target_compile_definitions(unit_tests_runtime PRIVATE UNITS_UDLS=1)
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     target_compile_options(unit_tests_runtime PRIVATE
diff --git a/test/unit_test/static/CMakeLists.txt b/test/unit_test/static/CMakeLists.txt
index f3981ce4..95ed6048 100644
--- a/test/unit_test/static/CMakeLists.txt
+++ b/test/unit_test/static/CMakeLists.txt
@@ -37,6 +37,7 @@ target_link_libraries(unit_tests_static_truncating PRIVATE
 target_compile_options(unit_tests_static_truncating PRIVATE
     $<IF:$<CXX_COMPILER_ID:MSVC>,/wd4242 /wd4244,-Wno-conversion>
 )
+target_compile_definitions(unit_tests_static_truncating PRIVATE UNITS_UDLS=1)
 
 add_library(unit_tests_static
     cgs_test.cpp
@@ -73,3 +74,4 @@ target_link_libraries(unit_tests_static PRIVATE
     unit_tests_static_truncating
     mp-units::mp-units
 )
+target_compile_definitions(unit_tests_static PRIVATE UNITS_UDLS=1)