Willem P. de Roever Hans Langmaack Amir Pnueli Compositionality: The Significant Difference, International Symposium, COMPOS'97, Bad Malente, Germany, September 8-12, 1997. Revised Lectures COMPOS Lecture Notes in Computer Science 1536 Springer 1998 3-540-65493-3 db/conf/compos/compos1997.html