+\author{Ferruccio Guidi%
+\thanks{This work has been partially supported by
+MoWGLI (European FET Project IST-2001-33562).}
+}
+
+\institute{Department of Computer Science\\
+Mura Anteo Zamboni 7, 40127 Bologna, ITALY.\\
+\email{fguidi@cs.unibo.it}}