Tatsuya Abe A Concurrent System of Multi-ported Processes with Causal Dependency. 146-162 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3302&spage=146 2004 conf/aplas/2004 APLAS db/conf/aplas/aplas2004.html#Abe04