Issue #10875: Update Regular Expression HOWTO; additional backport.
diff --git a/Doc/howto/regex.rst b/Doc/howto/regex.rst
index 711a0d5..8f39eeb 100644
--- a/Doc/howto/regex.rst
+++ b/Doc/howto/regex.rst
@@ -107,7 +107,10 @@
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 bytes 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]``.