-. (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.
MLA引文-. Proceedings the Twentieth Annual Convention. Ikatan Ahli Geologi Indonesia, 1991.
警告：這些引文格式不一定是100％准確.