Nicoletta Fornara Francesco Viganò Mario Verdicchio Marco Colombetti Artificial institutions: a model of institutional reality for open multiagent systems. 89-105 2008 16 Artif. Intell. Law 1 http://dx.doi.org/10.1007/s10506-007-9055-z db/journals/ail/ail16.html#FornaraVVC08