A Profitable Theory of nonmonotonic multiple inheritance based on Weighted Inheritance Networks C.T.I. Technical Report TR 93.07.30 - Βουτσινάς, Βασίλειος; Παυλίδης, Γεώργιος (Computer Technology Institute Computer Science and Engineering Department, Patras University Ινστιτούτο Τεχνολογίας Υπολογιστών, 1993)