Routledge, 2000
Buku Teks
Sargent, Lyman Tower
Brooks Cole, 1990
Buku Teks SO
Bullard, Reader
Oxford university Press, 1958
Buku Teks SO
edited by Reinhard Bendix
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Buku Teks SO
edited by George T. Crane and Abla Amawi
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Buku Teks SO