diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt
index 636b6d42..db8a2871 100644
--- a/docs/CMakeLists.txt
+++ b/docs/CMakeLists.txt
@@ -104,10 +104,24 @@ add_custom_command(OUTPUT "${SPHINX_INDEX_FILE}"
                        "${CMAKE_CURRENT_SOURCE_DIR}/introduction.rst"
                        "${CMAKE_CURRENT_SOURCE_DIR}/quick_start.rst"
 
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/concepts.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/customization_points.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/functions.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/metafunctions.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/concepts.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/customization_points.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/functions.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/metafunctions.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/dimensions.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/prefixes.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/quantity.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/units.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/utilities.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/utilities/basic_fixed_string.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/utilities/basic_symbol_text.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/core/types/utilities/ratio.rst"
+
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/math.rst"
+                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/random.rst"
+
                        "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems.rst"
 
                        "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/data.rst"
@@ -199,16 +213,6 @@ add_custom_command(OUTPUT "${SPHINX_INDEX_FILE}"
                        "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/us.rst"
                        "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/us/length.rst"
 
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/dimensions.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/prefixes.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/quantity.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/units.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/utilities.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/utilities/basic_fixed_string.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/utilities/basic_symbol_text.rst"
-                       "${CMAKE_CURRENT_SOURCE_DIR}/reference/types/utilities/ratio.rst"
-
                        "${CMAKE_CURRENT_SOURCE_DIR}/use_cases.rst"
                        "${CMAKE_CURRENT_SOURCE_DIR}/use_cases/custom_representation_types.rst"
                        "${CMAKE_CURRENT_SOURCE_DIR}/use_cases/extensions.rst"
diff --git a/docs/index.rst b/docs/index.rst
index e319b563..a89a1749 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -32,15 +32,13 @@ with a permissive `MIT license <https://github.com/mpusz/units/blob/master/LICEN
     faq
 
 .. toctree::
-    :maxdepth: 1
+    :maxdepth: 2
     :caption: Reference:
 
-    reference/concepts
-    reference/types
-    reference/functions
-    reference/metafunctions
-    reference/customization_points
+    reference/core
     reference/systems
+    reference/math
+    reference/random
 
 .. note::
 
diff --git a/docs/reference/core.rst b/docs/reference/core.rst
new file mode 100644
index 00000000..5cb6a914
--- /dev/null
+++ b/docs/reference/core.rst
@@ -0,0 +1,11 @@
+Core Library
+============
+
+.. toctree::
+    :maxdepth: 1
+
+    core/concepts
+    core/types
+    core/functions
+    core/metafunctions
+    core/customization_points
diff --git a/docs/reference/concepts.rst b/docs/reference/core/concepts.rst
similarity index 100%
rename from docs/reference/concepts.rst
rename to docs/reference/core/concepts.rst
diff --git a/docs/reference/customization_points.rst b/docs/reference/core/customization_points.rst
similarity index 100%
rename from docs/reference/customization_points.rst
rename to docs/reference/core/customization_points.rst
diff --git a/docs/reference/core/functions.rst b/docs/reference/core/functions.rst
new file mode 100644
index 00000000..edef5b40
--- /dev/null
+++ b/docs/reference/core/functions.rst
@@ -0,0 +1,4 @@
+Functions
+=========
+
+.. doxygenfunction:: units::quantity_cast
diff --git a/docs/reference/metafunctions.rst b/docs/reference/core/metafunctions.rst
similarity index 100%
rename from docs/reference/metafunctions.rst
rename to docs/reference/core/metafunctions.rst
diff --git a/docs/reference/types.rst b/docs/reference/core/types.rst
similarity index 100%
rename from docs/reference/types.rst
rename to docs/reference/core/types.rst
diff --git a/docs/reference/types/dimensions.rst b/docs/reference/core/types/dimensions.rst
similarity index 100%
rename from docs/reference/types/dimensions.rst
rename to docs/reference/core/types/dimensions.rst
diff --git a/docs/reference/types/prefixes.rst b/docs/reference/core/types/prefixes.rst
similarity index 100%
rename from docs/reference/types/prefixes.rst
rename to docs/reference/core/types/prefixes.rst
diff --git a/docs/reference/types/quantity.rst b/docs/reference/core/types/quantity.rst
similarity index 100%
rename from docs/reference/types/quantity.rst
rename to docs/reference/core/types/quantity.rst
diff --git a/docs/reference/types/units.rst b/docs/reference/core/types/units.rst
similarity index 100%
rename from docs/reference/types/units.rst
rename to docs/reference/core/types/units.rst
diff --git a/docs/reference/types/utilities.rst b/docs/reference/core/types/utilities.rst
similarity index 100%
rename from docs/reference/types/utilities.rst
rename to docs/reference/core/types/utilities.rst
diff --git a/docs/reference/types/utilities/basic_fixed_string.rst b/docs/reference/core/types/utilities/basic_fixed_string.rst
similarity index 100%
rename from docs/reference/types/utilities/basic_fixed_string.rst
rename to docs/reference/core/types/utilities/basic_fixed_string.rst
diff --git a/docs/reference/types/utilities/basic_symbol_text.rst b/docs/reference/core/types/utilities/basic_symbol_text.rst
similarity index 100%
rename from docs/reference/types/utilities/basic_symbol_text.rst
rename to docs/reference/core/types/utilities/basic_symbol_text.rst
diff --git a/docs/reference/types/utilities/ratio.rst b/docs/reference/core/types/utilities/ratio.rst
similarity index 100%
rename from docs/reference/types/utilities/ratio.rst
rename to docs/reference/core/types/utilities/ratio.rst
diff --git a/docs/reference/functions.rst b/docs/reference/math.rst
similarity index 54%
rename from docs/reference/functions.rst
rename to docs/reference/math.rst
index bb209253..b3f30d09 100644
--- a/docs/reference/functions.rst
+++ b/docs/reference/math.rst
@@ -1,14 +1,5 @@
-Functions
-=========
-
-Casting and Converions
-----------------------
-
-.. doxygenfunction:: units::quantity_cast
-
-
 Math
-----
+====
 
 .. doxygenfunction:: units::pow
 
diff --git a/docs/reference/random.rst b/docs/reference/random.rst
new file mode 100644
index 00000000..ad168c2d
--- /dev/null
+++ b/docs/reference/random.rst
@@ -0,0 +1,40 @@
+Random
+======
+
+.. doxygenstruct:: units::uniform_int_distribution
+
+.. doxygenstruct:: units::uniform_real_distribution
+
+.. doxygenstruct:: units::binomial_distribution
+
+.. doxygenstruct:: units::negative_binomial_distribution
+
+.. doxygenstruct:: units::geometric_distribution
+
+.. doxygenstruct:: units::poisson_distribution
+
+.. doxygenstruct:: units::exponential_distribution
+
+.. doxygenstruct:: units::gamma_distribution
+
+.. doxygenstruct:: units::weibull_distribution
+
+.. doxygenstruct:: units::extreme_value_distribution
+
+.. doxygenstruct:: units::normal_distribution
+
+.. doxygenstruct:: units::lognormal_distribution
+
+.. doxygenstruct:: units::chi_squared_distribution
+
+.. doxygenstruct:: units::cauchy_distribution
+
+.. doxygenstruct:: units::fisher_f_distribution
+
+.. doxygenstruct:: units::student_t_distribution
+
+.. doxygenstruct:: units::discrete_distribution
+
+.. doxygenstruct:: units::piecewise_constant_distribution
+
+.. doxygenstruct:: units::piecewise_linear_distribution