Oberlander, T. M., & Muller, R. A. (1987). Essentials of physical geography today (2nd ed.). Random House.
Cita Chicago (17th ed.)Oberlander, Theodore M., i Robert A. Muller. Essentials of Physical Geography Today. 2nd ed. New York: Random House, 1987.
Cita MLA (9th ed.)Oberlander, Theodore M., i Robert A. Muller. Essentials of Physical Geography Today. 2nd ed. Random House, 1987.
Atenció: Aquestes cites poden no estar 100% correctes.