Não informado. (1967). Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Earth and Mineral Sciences. University Park, Pa: Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Earth and Mineral Sciences. Pennsylvania State College, College of Earth and Mineral Sciences, 1967.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.