The Identifiers and keywords syntax diagram did not appear correctly in the

HTML output. I've now fixed this as best I can (but could do with
improvement).

Note that there are two terms used, "Other_ID_Start" and
"Other_ID_Continue" that are not explained; I've added an extra see
reference to PEP 3131 though.

Doc/reference/lexical_analysis.rst

@@ -286,10 +286,8 @@ Identifiers are unlimited in length.  Case is significant.
 
 .. productionlist::
    identifier: `id_start` `id_continue`*
-   id_start: <all characters in general categories Lu, Ll, Lt, Lm, Lo, Nl,
-              the underscore, and characters with the Other_ID_Start property>
-   id_continue: <all characters in `id_start`, plus characters in the categories
-                 Mn, Mc, Nd, Pc and others with the Other_ID_Continue property>
+   id_start: <all characters in general categories Lu, Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the Other_ID_Start property>
+   id_continue: <all characters in `id_start`, plus characters in the categories Mn, Mc, Nd, Pc and others with the Other_ID_Continue property>
 
 The Unicode category codes mentioned above stand for:
 
@@ -311,6 +309,8 @@ A non-normative HTML file listing all valid identifier characters for Unicode
 4.1 can be found at
 http://www.dcl.hpi.uni-potsdam.de/home/loewis/table-3131.html.
 
+See :pep:`3131` for further details.
+
 .. _keywords:
 
 Keywords