Robert Colvin Lindsay Groves Ian J. Hayes David Hemer Ray Nickson Paul A. Strooper Developing Logic Programs from Specifications Using Stepwise Refinement. 66-89 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3049&spage=66 2004 conf/lopstr/2004lncs Program Development in Computational Logic db/conf/lopstr/lncs3049.html#ColvinGHHNS04