Jan-Willem G. M. Hubbers Arthur H. M. ter Hofstede Formalization of Communication and Behaviour in Object-Oriented Analysis. 147-183 1997 23 Data Knowl. Eng. 2 db/journals/dke/dke23.html#HubbersH97 http://dx.doi.org/10.1016/S0169-023X(96)00039-0