diff --git a/hg-fast-export.txt b/hg-fast-export.txt
index 8b33520..0568597 100644
--- a/hg-fast-export.txt
+++ b/hg-fast-export.txt
@@ -30,6 +30,17 @@ hg-fast-export'ed from mercurial:
 will give hints on which branches need adjustment for starting over
 again.
 
+As mercurial appears to be much less picky about the syntax of the
+author information than git, an author mapping file can be given to
+hg-fast-export to fix up malformed author strings. The file is
+specified using the -A option. The file should contain lines of the
+form "FromAuthor=ToAuthor". The example authors.map below will
+translate "User <garbage<user@example.com>" to "User <user@example.com>".
+
+-- Start of authors.map --
+User <garbage<user@example.com>=User <user@example.com>
+-- End of authors.map --
+
 Notes/Limitations
 =================