Sergey Buffalov Khaled El-Fakih Nina Yevtushenko Gregor von Bochmann Progressive Solutions to a Parallel Automata Equation. 367-382 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2767&spage=367 2003 conf/forte/2003 FORTE db/conf/forte/forte2003.html#BuffalovEYB03