Não informado. (1967). Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Earth and Mineral Sciences. University Park, Pa: Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
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