Leavitt, Fred
Research methods for behavioral scientists
C. Brown Publishers , 1991
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Denscombe, Martyn
Research proposals: a practical guide
Open University Press, 2012
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Denscombe, Martyn
Research Proposals a Pratical guide
Mc Graw Hill, 2012
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Sommer, Robert
Behavioral research: Tools and techniques
New York, 2002
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Causal models in the social sciences
edited by H.M. Blalock
Aldine Publishing, 1974
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