Schewe, Klaus-Dieter, and Bernhard Thalheim. “Fundamental Concepts of Object Oriented Databases”. Acta Cybernetica 11, no. 1-2 (January 1, 1993): 49-83. Accessed April 25, 2024. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3420.