Andrew A. Fisher, John E. Laing, John E. Stoeckel, John W. Townsend
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The Population Council, 998
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Everest, Suzanne
Bailliere Tindall , 1998
Buku Teks
edited by Nancy Loudon
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Buku Referensi
Russ, Thomas H.
McGraw-Hill, 2009
Buku Teks