@techreport{eprints137,
            type = {Working Paper},
       booktitle = {38th International Colloquium on Automata, Languages and Programming (ICALP?11)},
           title = {Constraints for Service Contracts},
     institution = {IMT Institute for Advanced Studies Lucca},
          author = {Maria Grazia Buscemi and Mario Coppo and Mariangiola Dezani-Ciancaglini and Ugo Montanari},
            year = {2011},
             url = {http://eprints.imtlucca.it/137/}
}