diff --git a/doc/asterisk.tex b/doc/asterisk.tex
index f9557bf601..86a50ff806 100644
--- a/doc/asterisk.tex
+++ b/doc/asterisk.tex
@@ -2,6 +2,8 @@
 % dependencies for it.  Then, run:
 %
 % rubber asterisk.tex
+%
+% http://www.pps.jussieu.fr/~beffara/soft/rubber/
 
 \documentclass[12pt,a4]{report}
 \usepackage{hyperref}