Barbey, S.; Kempe, M.; Strohmeier, A. (1993). "Object-Oriented Programming with Ada 9X". Draft Technical Report. Swiss Federal Institute of Technology in Lausanne Software Engineering Laboratory. Retrieved 15 December 2013. Ada 83 itself is generally not considered to be object-oriented; rather, according to the terminology of Wegner [Weg 87], it is said to be object-based, since it provides only a restricted form of inheritance and it lacks polymorphism. http://www.adahome.com/9X/OOP-Ada9X.html