Não informado. (1931). Mineral Industries. Pennsylvania State College, College of Earth and Mineral Sciences.
Cita Chicago Style (17a ed.)Não informado. Mineral Industries. State College, Pa: Pennsylvania State College, College of Earth and Mineral Sciences, 1931.
Cita MLA (8a ed.)Não informado. Mineral Industries. Pennsylvania State College, College of Earth and Mineral Sciences, 1931.
Precaución: Estas citas no son 100% exactas.