Gower, 1991
Buku Referensi
Muir, Robert, author
Henry Frowde, Hodder & Stoughton, 1921
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Markus, John, 1911-, author
McGraw-Hill, 1971
Buku Referensi
Leslie D. "Doc" Long, Clifford Gordon, Charles F. Peck, Jack R. Benjamin
McGraw-Hill, 1982
Buku Referensi
Hurlbut, Cornelius S., author
John Wiley & Sons, 1977
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