Issue #10875: Update Regular Expression HOWTO; additional backport with 2.7 modification.
diff --git a/Doc/howto/regex.rst b/Doc/howto/regex.rst
index 49cd65e..1005c23 100644
--- a/Doc/howto/regex.rst
+++ b/Doc/howto/regex.rst
@@ -112,7 +112,10 @@
Some of the special sequences beginning with ``'\'`` represent predefined sets
of characters that are often useful, such as the set of digits, the set of
letters, or the set of anything that isn't whitespace. The following predefined
-special sequences are available:
+special sequences are a subset of those available. The equivalent classes are
+for byte string patterns. For a complete list of sequences and expanded class
+definitions for Unicode string patterns, see the last part of
+:ref:`Regular Expression Syntax <re-syntax>`.
``\d``
Matches any decimal digit; this is equivalent to the class ``[0-9]``.