Não informado. (1967). Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences.
Chicago-referens (17:e uppl.)Não informado. Earth and Mineral Sciences. University Park, Pa: Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
MLA-referens (8:e uppl.)Não informado. Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.