Bove, Mary
An Encycloprdis of Natural Healing for Children and Infants
Keats Publishing, 2001
 Buku Teks
Cook, Peter, 1936
Primer
Academy Editions, 1996
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Churchill, Gilbert A.
Marketing research : methodological foundations
The Dryden Press, 1995
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Churchill, Gilbert A.
Marketing research : methodological foundations
Thomson, 2005
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Systems research : methodological problems
edited by J.M. Gvishiani
Pergamon Press, 1984
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