Remove extra verb; reported by Detlef Lannert.
diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex
index aaa282e..26fbb5e 100644
--- a/Doc/lib/libre.tex
+++ b/Doc/lib/libre.tex
@@ -303,8 +303,7 @@
\dfn{negative lookbehind assertion}. Similar to positive lookbehind
assertions, the contained pattern must only match strings of some
fixed length. Patterns which start with negative lookbehind
-assertions will may match at the beginning of the string being
-searched.
+assertions may match at the beginning of the string being searched.
\end{list}