Help: Provide backreferences.

Short intro to pages cmake-variables.7 and cmake-env-variables.7,
with backlinks to cmake-language.7.

Help/manual/cmake-env-variables.7.rst

@@ -7,6 +7,14 @@ cmake-env-variables(7)
 
    .. contents::
 
+This page lists environment variables that have special
+meaning to CMake.
+
+For general information on environment variables, see the
+:ref:`Environment Variables <CMake Language Environment Variables>`
+section in the cmake-language manual.
+
+
 Environment Variables that Control the Build
 ============================================
 

Help/manual/cmake-language.7.rst

@@ -557,11 +557,11 @@ Otherwise, the variable reference evaluates to an empty string.
 The ``$CACHE{VAR}`` syntax can be used to do direct cache entry
 lookups.
 
-The :manual:`cmake-variables(7)` manual documents many variables
+The :manual:`cmake-variables(7)` manual documents the many variables
 that are provided by CMake or have meaning to CMake when set
 by project code.
 
-.. _`CMake Language Lists`:
+.. _`CMake Language Environment Variables`:
 
 Environment Variables
 =====================
@@ -589,6 +589,7 @@ Initialization
 The :manual:`cmake-env-variables(7)` manual documents environment
 variables that have special meaning to CMake.
 
+.. _`CMake Language Lists`:
 
 Lists
 =====

Help/manual/cmake-variables.7.rst

@@ -7,6 +7,14 @@ cmake-variables(7)
 
    .. contents::
 
+This page  documents variables that are provided by CMake
+or have meaning to CMake when set by project code.
+
+For general information on variables, see the
+:ref:`Variables <CMake Language Variables>`
+section in the cmake-language manual.
+
+
 Variables that Provide Information
 ==================================