diff --git a/example/alternative_namespaces/box_example.cpp b/example/alternative_namespaces/box_example.cpp
index bdfb4038..18e597a9 100644
--- a/example/alternative_namespaces/box_example.cpp
+++ b/example/alternative_namespaces/box_example.cpp
@@ -1,4 +1,5 @@
 
+#include <units/quantity_io.h>
 #include "./length.h"
 #include "./acceleration.h"
 #include "./density.h"
diff --git a/example/alternative_namespaces/capacitor_time_curve.cpp b/example/alternative_namespaces/capacitor_time_curve.cpp
index c6590808..6d833d16 100644
--- a/example/alternative_namespaces/capacitor_time_curve.cpp
+++ b/example/alternative_namespaces/capacitor_time_curve.cpp
@@ -24,6 +24,7 @@
 #include <units/physical/si/derived/resistance.h>
 #include <units/physical/si/base/time.h>
 #include <units/math.h>
+#include <units/quantity_io.h>
 #include "./voltage.h"
 #include <iostream>
 
diff --git a/example/alternative_namespaces/clcpp_response.cpp b/example/alternative_namespaces/clcpp_response.cpp
index a7c4c2fc..ac2336ba 100644
--- a/example/alternative_namespaces/clcpp_response.cpp
+++ b/example/alternative_namespaces/clcpp_response.cpp
@@ -17,6 +17,7 @@
 
 #include <iostream>
 #include <units/format.h>
+#include <units/quantity_io.h>
 
 #include "./length.h"
 #include "./volume.h"
diff --git a/example/alternative_namespaces/conversion_factor.cpp b/example/alternative_namespaces/conversion_factor.cpp
index 6c5a46b3..685f45b4 100644
--- a/example/alternative_namespaces/conversion_factor.cpp
+++ b/example/alternative_namespaces/conversion_factor.cpp
@@ -18,6 +18,7 @@
 
 #include "./units_str.h"
 #include "./length.h"
+#include <units/quantity_io.h>
 #include <iostream>
 
 /*
diff --git a/example/alternative_namespaces/timer.cpp b/example/alternative_namespaces/timer.cpp
index 520a1f72..50bd4984 100644
--- a/example/alternative_namespaces/timer.cpp
+++ b/example/alternative_namespaces/timer.cpp
@@ -1,4 +1,5 @@
 
+#include <units/quantity_io.h>
 #include <iostream>
 #include "./timer.h"
 
diff --git a/example/avg_speed.cpp b/example/avg_speed.cpp
index cde2eb99..48c68fb2 100644
--- a/example/avg_speed.cpp
+++ b/example/avg_speed.cpp
@@ -23,6 +23,7 @@
 #include <units/physical/si/cgs/derived/speed.h>
 #include <units/physical/si/international/derived/speed.h>
 #include <units/physical/si/derived/speed.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
diff --git a/example/box_example.cpp b/example/box_example.cpp
index 6ebafbe2..00923a81 100644
--- a/example/box_example.cpp
+++ b/example/box_example.cpp
@@ -7,6 +7,7 @@
 #include <units/physical/si/base/time.h>
 #include <units/physical/si/derived/volume.h>
 #include <units/format.h>
+#include <units/quantity_io.h>
 #include <cassert>
 
 namespace {
diff --git a/example/capacitor_time_curve.cpp b/example/capacitor_time_curve.cpp
index b08a0da4..677f875f 100644
--- a/example/capacitor_time_curve.cpp
+++ b/example/capacitor_time_curve.cpp
@@ -25,6 +25,7 @@
 #include <units/physical/si/base/time.h>
 #include <units/physical/si/derived/voltage.h>
 #include <units/math.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 int main()
diff --git a/example/clcpp_response.cpp b/example/clcpp_response.cpp
index 37bace5a..e32037b8 100644
--- a/example/clcpp_response.cpp
+++ b/example/clcpp_response.cpp
@@ -25,6 +25,7 @@
 #include <units/physical/si/typographic/base/length.h>
 #include <units/physical/si/us/base/length.h>
 #include <units/physical/si/derived/volume.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
diff --git a/example/conversion_factor.cpp b/example/conversion_factor.cpp
index 0df01fa4..1e0b45a1 100644
--- a/example/conversion_factor.cpp
+++ b/example/conversion_factor.cpp
@@ -17,6 +17,7 @@
 
 #include <units/physical/si/base/length.h>
 #include <units/format.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 /*
diff --git a/example/custom_systems.cpp b/example/custom_systems.cpp
index d4e73e24..ea2c47ba 100644
--- a/example/custom_systems.cpp
+++ b/example/custom_systems.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/quantity.h>
+#include <units/quantity_io.h>
 #include <units/physical/si/prefixes.h>
 #include <iostream>
 
diff --git a/example/experimental_angle.cpp b/example/experimental_angle.cpp
index 19ae993f..49f17054 100644
--- a/example/experimental_angle.cpp
+++ b/example/experimental_angle.cpp
@@ -25,6 +25,7 @@
 #include <units/physical/si/base/length.h>
 #include <units/physical/si/derived/energy.h>
 #include <units/physical/si/derived/torque.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 using namespace units;
diff --git a/example/hello_units.cpp b/example/hello_units.cpp
index 1c907134..71b45e4f 100644
--- a/example/hello_units.cpp
+++ b/example/hello_units.cpp
@@ -23,6 +23,7 @@
 #include <units/format.h>
 #include <units/physical/si/international/derived/speed.h>
 #include <units/physical/si/derived/speed.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 using namespace units::physical;
diff --git a/example/linear_algebra.cpp b/example/linear_algebra.cpp
index 6dfe06c9..119cd30f 100644
--- a/example/linear_algebra.cpp
+++ b/example/linear_algebra.cpp
@@ -24,13 +24,14 @@
 #include <units/physical/si/derived/force.h>
 #include <units/physical/si/derived/energy.h>
 #include <units/format.h>
+#include <units/quantity_io.h>
 #include <linear_algebra.hpp>
 #include <iostream>
 
-namespace {
+namespace STD_LA {
 
 template<class ET, class OT>
-std::ostream& operator<<(std::ostream& os, const std::math::vector<ET, OT>& v)
+std::ostream& operator<<(std::ostream& os, const vector<ET, OT>& v)
 {
   os << "|";
   for (auto i = 0U; i < v.size(); ++i) {
@@ -41,7 +42,7 @@ std::ostream& operator<<(std::ostream& os, const std::math::vector<ET, OT>& v)
 }
 
 template<class ET, class OT>
-std::ostream& operator<<(std::ostream& os, const std::math::matrix<ET, OT>& v)
+std::ostream& operator<<(std::ostream& os, const matrix<ET, OT>& v)
 {
   for (auto i = 0U; i < v.rows(); ++i) {
     os << "|";
@@ -53,6 +54,9 @@ std::ostream& operator<<(std::ostream& os, const std::math::matrix<ET, OT>& v)
   return os;
 }
 
+}  // namespace STD_LA
+
+namespace {
 
 using namespace units::physical;
 using namespace units::physical::si::literals;
@@ -345,7 +349,7 @@ void quantity_of_matrix_tests()
   quantity_of_matrix_divide_by_scalar();
 }
 
-}
+}  // namespace
 
 int main()
 {
diff --git a/example/measurement.cpp b/example/measurement.cpp
index 2ab40053..cc42c436 100644
--- a/example/measurement.cpp
+++ b/example/measurement.cpp
@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 #include <units/physical/si/derived/acceleration.h>
+#include <units/quantity_io.h>
 #include <cmath>
 #include <compare>
 #include <iostream>
diff --git a/example/total_energy.cpp b/example/total_energy.cpp
index fff77463..8bc0de90 100644
--- a/example/total_energy.cpp
+++ b/example/total_energy.cpp
@@ -26,6 +26,7 @@
 #include <units/physical/si/derived/speed.h>
 #include <units/physical/si/constants.h>
 #include <units/math.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
diff --git a/example/unknown_dimension.cpp b/example/unknown_dimension.cpp
index 19c527e2..9d898423 100644
--- a/example/unknown_dimension.cpp
+++ b/example/unknown_dimension.cpp
@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 #include <units/physical/si/derived/speed.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
diff --git a/src/include/units/bits/external/fixed_string.h b/src/include/units/bits/external/fixed_string.h
index 18adc0bd..9a20954a 100644
--- a/src/include/units/bits/external/fixed_string.h
+++ b/src/include/units/bits/external/fixed_string.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/bits/external/hacks.h>
-#include <algorithm>
 #include <cstdlib>
-#include <ostream>
 #include <compare>
 
+// TODO use <algorithm> when moved to C++20 modules (parsing takes too long for each translation unit)
+
 namespace units {
 
 /**
@@ -52,14 +52,15 @@ struct basic_fixed_string {
   }
 
   [[nodiscard]] constexpr std::size_t size() const noexcept { return N; }
-  [[nodiscard]] constexpr const CharT* c_str() const noexcept { return data_; }
-  [[nodiscard]] constexpr const CharT& operator[](std::size_t index) const noexcept { return data_[index]; }
-  [[nodiscard]] constexpr CharT operator[](std::size_t index) noexcept { return data_[index]; }
+  [[nodiscard]] constexpr const CharT* data() const noexcept { return data_; }
+  [[nodiscard]] constexpr const CharT* c_str() const noexcept { return data(); }
+  [[nodiscard]] constexpr const CharT& operator[](std::size_t index) const noexcept { return data()[index]; }
+  [[nodiscard]] constexpr CharT operator[](std::size_t index) noexcept { return data()[index]; }
 
-  [[nodiscard]] constexpr iterator begin() noexcept { return std::begin(data_); }
-  [[nodiscard]] constexpr const_iterator begin() const noexcept { return std::begin(data_); }
-  [[nodiscard]] constexpr iterator end() noexcept { return std::end(data_); }
-  [[nodiscard]] constexpr const_iterator end() const noexcept { return std::end(data_); }
+  [[nodiscard]] constexpr iterator begin() noexcept { return data(); }
+  [[nodiscard]] constexpr const_iterator begin() const noexcept { return data(); }
+  [[nodiscard]] constexpr iterator end() noexcept { return data() + size(); }
+  [[nodiscard]] constexpr const_iterator end() const noexcept { return data() + size(); }
 
   template<std::size_t N2>
   [[nodiscard]] constexpr friend basic_fixed_string<CharT, N + N2> operator+(
@@ -75,7 +76,14 @@ struct basic_fixed_string {
 
   [[nodiscard]] constexpr bool operator==(const basic_fixed_string& other) const
   {
-    return std::ranges::equal(*this, other);
+    if (size() != other.size())
+      return false;
+    for (size_t i = 0; i != size(); ++i) {
+      if ((*this)[i] != other[i])
+        return false;
+    }
+    return true;
+    // return std::ranges::equal(*this, other);
   }
 
   template<std::size_t N2>
@@ -84,14 +92,20 @@ struct basic_fixed_string {
   template<std::size_t N2>
   [[nodiscard]] friend constexpr auto operator<=>(const basic_fixed_string& lhs, const basic_fixed_string<CharT, N2>& rhs)
   {
-    return std::lexicographical_compare_three_way(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
-  }
+    auto first1 = lhs.begin();
+    const auto last1 = lhs.end();
+    auto first2 = rhs.begin();
+    const auto last2 = rhs.end();
+    auto comp = std::compare_three_way();
 
-  template<class Traits>
-  friend std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os,
-                                                       const basic_fixed_string& txt)
-  {
-    return os << txt.c_str();
+    for (; first1 != last1 && first2 != last2; ++first1, ++first2)
+      if (auto cmp = comp(*first1, *first2); cmp != 0)
+        return cmp;
+ 
+    return first1 != last1 ? std::strong_ordering::greater :
+           first2 != last2 ? std::strong_ordering::less :
+                             std::strong_ordering::equal;
+    // return std::lexicographical_compare_three_way(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
   }
 };
 
diff --git a/src/include/units/bits/external/fixed_string_io.h b/src/include/units/bits/external/fixed_string_io.h
new file mode 100644
index 00000000..59728791
--- /dev/null
+++ b/src/include/units/bits/external/fixed_string_io.h
@@ -0,0 +1,36 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/external/fixed_string.h>
+#include <ostream>
+
+namespace units {
+
+template<typename CharT, class Traits, std::size_t N>
+std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const basic_fixed_string<CharT, N>& txt)
+{
+  return os << txt.c_str();
+}
+
+}  // namespace units
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index df6fcc25..3fda0cc2 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -314,21 +314,6 @@ public:
 #endif
 
   [[nodiscard]] friend constexpr bool operator==(const quantity& lhs, const quantity& rhs) = default;
-
-  template<class CharT, class Traits>
-  friend std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const quantity& q)
-    requires requires { os << q.count(); }
-  {
-    if(os.width()) {
-      // std::setw() applies to the whole quantity output so it has to be first put into std::string
-      std::basic_ostringstream<CharT, Traits> s;
-      detail::to_stream(s, q);
-      return os << s.str();
-    }
-
-    detail::to_stream(os, q);
-    return os;
-  }
 };
 
 // CTAD
diff --git a/src/include/units/quantity_io.h b/src/include/units/quantity_io.h
new file mode 100644
index 00000000..beb3edf7
--- /dev/null
+++ b/src/include/units/quantity_io.h
@@ -0,0 +1,46 @@
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/external/fixed_string_io.h>
+#include <units/quantity.h>
+
+namespace units {
+
+template<typename CharT, typename Traits, typename D, typename U, typename Rep>
+std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const quantity<D, U, Rep>& q)
+  requires requires { os << q.count(); }
+{
+  if(os.width()) {
+    // std::setw() applies to the whole quantity output so it has to be first put into std::string
+    std::basic_ostringstream<CharT, Traits> s;
+    detail::to_stream(s, q);
+    return os << s.str();
+  }
+
+  detail::to_stream(os, q);
+  return os;
+}
+
+}  // namespace units
diff --git a/test/unit_test/runtime/digital_info_test.cpp b/test/unit_test/runtime/digital_info_test.cpp
index beea87f7..d1f269dc 100644
--- a/test/unit_test/runtime/digital_info_test.cpp
+++ b/test/unit_test/runtime/digital_info_test.cpp
@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 #include <units/data/data.h>
+#include <units/quantity_io.h>
 #include <catch2/catch.hpp>
 #include <sstream>
 
diff --git a/test/unit_test/runtime/fmt_test.cpp b/test/unit_test/runtime/fmt_test.cpp
index 683c0491..0ce466f5 100644
--- a/test/unit_test/runtime/fmt_test.cpp
+++ b/test/unit_test/runtime/fmt_test.cpp
@@ -20,10 +20,11 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/format.h"
-#include "units/math.h"
-#include "units/physical/si/si.h"
-#include "units/physical/si/cgs/cgs.h"
+#include <units/format.h>
+#include <units/math.h>
+#include <units/physical/si/si.h>
+#include <units/physical/si/cgs/cgs.h>
+#include <units/quantity_io.h>
 #include <catch2/catch.hpp>
 #include <iomanip>
 #include <sstream>
diff --git a/test_package/test_package.cpp b/test_package/test_package.cpp
index b4fabcb5..c3097598 100644
--- a/test_package/test_package.cpp
+++ b/test_package/test_package.cpp
@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 #include <units/physical/si/derived/speed.h>
+#include <units/quantity_io.h>
 #include <iostream>
 
 using namespace units;