@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}
}