Correct typo
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 6a82d1b..e8a6ccd 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -31,7 +31,7 @@
A triple (repo, branch, version) representing the Subversion
information of the Python interpreter.
\var{repo} is the name of the repository, \code{'CPython'}.
- \var{branch} is the a string of one of the forms \code{'trunk'},
+ \var{branch} is a string of one of the forms \code{'trunk'},
\code{'branches/name'} or \code{'tags/name'}.
\var{version} is the output of \code{svnversion}, if the
interpreter was built from a Subversion checkout; it contains