Guilin Qi Peter Milligan Paul Sage Incidence Calculus on Lukasiewicz's Three-valued Logic. 357-378 2005 68 Fundam. Inform. 4 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=68&issue=4&spage=357 db/journals/fuin/fuin68.html#QiMS05