Fixed index references to modules.
diff --git a/Doc/lib/libcopy.tex b/Doc/lib/libcopy.tex
index 8f5e03c..d07121e 100644
--- a/Doc/lib/libcopy.tex
+++ b/Doc/lib/libcopy.tex
@@ -75,7 +75,7 @@
 \code{__getinitargs__()}, \code{__getstate__()} and
 \code{__setstate__()}.  See the description of module \code{pickle}
 for information on these methods.
-\stmodindex{pickle}
+\refstmodindex{pickle}
 \renewcommand{\indexsubitem}{(copy protocol)}
 \ttindex{__getinitargs__}
 \ttindex{__getstate__}