Babbie, Earl R., author
Wadsworth and Cengage Learning, 2013 (Student Edition)
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Babbie, Earl R., author
Wadsworth and Cengage Learning, 2013 (International edition)
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May, Tim, author
Open University Press, 2001
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Judd, Charles M., author
Methuen, 1991
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Sjoberg, Gideon
Harper & Row Publishers, 1968
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