Till Mossakowski Horst Reichel Markus Roggenbach Lutz Schröder Algebraic-Coalgebraic Specification in Co Casl. 376-392 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2755&spage=376 2002 conf/wadt/2002 WADT db/conf/wadt/wadt2002.html#MossakowskiRRS02