Não informado. (1931). Mineral Industries. Pennsylvania State College, College of Earth and Mineral Sciences.
Style de citation Chicago (17e éd.)Não informado. Mineral Industries. State College, Pa: Pennsylvania State College, College of Earth and Mineral Sciences, 1931.
Style de citation MLA (8e éd.)Não informado. Mineral Industries. Pennsylvania State College, College of Earth and Mineral Sciences, 1931.
Attention : ces citations peuvent ne pas être correctes à 100%.