Husted, Gladys L., author
Mosby , 1995
Buku Teks
Husted, Gladys L., author
Mosby Year Book, 1989
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plous, Scott
McGraw-Hill, 1993
Buku Teks
Devettere, Raymond J.
Georgetown University Press, 1995
Buku Teks
Hawley, Georgina, author
Social Science Press, 1997
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