-. (1991). Proceedings the twentieth annual convention. Ikatan Ahli Geologi Indonesia.
Chicago Style (17th ed.) Citation-. Proceedings the Twentieth Annual Convention. Ikatan Ahli Geologi Indonesia, 1991.
Cita MLA-. Proceedings the Twentieth Annual Convention. Ikatan Ahli Geologi Indonesia, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.