Alberto Pettorossi Maurizio Proietti Program Transformation: Theoretical Foundations and Basic Techniques. Part 1. 2005 66 Fundam. Inform. 4 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=66&issue=4&spage=i db/journals/fuin/fuin66.html#PettorossiP05