English Language Services; editor, Charles J. Hirsch, James A. Curtin
Collier/Macmillan, 1971
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Puchta, Herbert
Cambridge University Press, 2014
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Pack, Alice C.
Newbury House Pub., 1980
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Pincas, Anita
Macmillan, 1983
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Harrison, G.B.
Penguin Books, 1953
Buku Teks SO