Kongreß of philosophy. (1973). Proceedings of the XVth [fifteenth] World Congress of Philosophy: 17th to 22nd september 1973, Varna (Bulgaria). Sofia Pr..
Chicago-viite (17. p.)Kongreß of philosophy. Proceedings of the XVth [fifteenth] World Congress of Philosophy: 17th to 22nd September 1973, Varna (Bulgaria). Sofia: Sofia Pr., 1973.
MLA-viite (8. p.)Kongreß of philosophy. Proceedings of the XVth [fifteenth] World Congress of Philosophy: 17th to 22nd September 1973, Varna (Bulgaria). Sofia Pr., 1973.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.