Vaughan, Terry A.
Saunders College, 1986
Buku Referensi
Nowak, Ronald M.
John Hopkins University Press, 1983
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Parker, Steve
Miles Kelly, 2000
Buku Referensi
Nowak, Ronald M.
John Hopkins University Press, 1983
Buku Referensi
Attenborough, David
BBC Worldwide Limited, 2004
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