Update markup for structure

Author: AA-Turner

documenting/markup.rst

@@ -6,6 +6,9 @@ reStructuredText Markup
 
 .. highlight::  rest
 
+This document describes the custom reStructuredText markup introduced by Sphinx
+to support Python documentation and how it should be used.
+
 
 .. _rst-primer:
 
@@ -190,7 +193,8 @@ A directive is a generic block of explicit markup.  Besides roles, it is one of
 the extension mechanisms of reST, and Sphinx makes heavy use of it.
 
 Basically, a directive consists of a name, arguments, options and content. (Keep
-this terminology in mind, it is used in the next chapter describing custom
+this terminology in mind, it is used in `:ref:`the next section
+<Additional Markup Constructs>` describing custom
 directives.)  Looking at this example,
 
 ::

documenting/start-documenting.rst

@@ -11,9 +11,7 @@ contributed by various authors. The markup used for the Python documentation is
 `reStructuredText`_, developed by the `docutils`_ project, amended by custom
 directives and using a toolset named `Sphinx`_ to post-process the HTML output.
 
-This document describes the style guide for our documentation as well as the
-custom reStructuredText markup introduced by Sphinx to support Python
-documentation and how it should be used.
+This document describes the style guide for our documentation.
 
 The documentation in HTML, PDF or EPUB format is generated from text files
 written using the :ref:`reStructuredText format <markup>` and contained in the