Lloyd, Lewis E.
Techniques for efficient research
Chemical Publishing Company, Inc., 1966
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Sommer, Robert
Behavioral research: Tools and techniques
New York, 2002
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Peterson, Sandra J.
Middle range theories: application to nursing research
J.B. Lippincott, 2004
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Maafs, Kurt-Jurgen
Bridges for research: range and impact of the Humboldt foundation
Alexander Von Humboldt Foundation , 1989
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Ferber, Robert
Statistical techniques in market research
McGraw-Hill, 1949
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