@inproceedings{Schr91b,
   author = {M.~Schrefl AND G.~Kappel},
   booktitle = {{Proceedings of the 10th International Conference on the Entity-Relationship Approach (ER `91), Participants Proceedings, San Mateo, Calif., U.S.A.}},
   editor = {T.J.~Teorey},
   month = oct,
   pages = {285--307},
   title = {{Cooperation Contracts}},
   year = {1991}
}
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