Umeshwar Dayal Frank Manola Alejandro P. Buchmann Upen S. Chakravarthy David Goldhirsch Sandra Heiler Jack A. Orenstein Arnon Rosenthal Simplifying Complex Objects: The PROBE Approach to Modelling and Querying Them. 17-37 1987 BTW db/conf/btw/btw87.html#DayalMBCGHOR87