Audun Jøsang Elizabeth Gray Michael Kinateder Simplification and analysis of transitive trust networks. 139-161 2006 4 Web Intelligence and Agent Systems 2 http://iospress.metapress.com/openurl.asp?genre=article&issn=1570-1263&volume=4&issue=2&spage=139 db/journals/wias/wias4.html#JosangGK06