Williams, Leonard Aimslie
American Elsevier Publishing Company, INC, 1968
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Williams, Leonard Aimslie
London Longmans, Green and Co. Ltd. 1967,
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edited by Charles P. Bonini, Robert K. Jaedicke and Harvey M. Wagner
McGraw-Hill, 1964
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Keller, kotler
Pearson Education, Inc, 2006
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Kotler, Philip
[publisher not identified], [date of publication not identified]
Buku Teks