Mariusz Nowostawski Martin K. Purvis Marcos De Oliveira Stephen Cranefield Institutions in the OPAL multi-agent system. 191-207 2006 17 Journal of Intelligent and Fuzzy Systems 3 http://iospress.metapress.com/openurl.asp?genre=article&issn=1064-1246&volume=17&issue=3&spage=191 db/journals/jifs/jifs17.html#NowostawskiPOC06