Guido Boella Leendert W. N. van der Torre Harko Verhagen Introduction to Normative Multiagent Systems. 1-7 2005 NORMAS http://www.aisb.org.uk/publications/proceedings/aisb05/8_Normas_Final.pdf conf/normas/2005 db/conf/normas/normas2005.html#BoellaTV05