Tull, D. S. &. H. D. I. (1960). Marketing Research: Measurment & Method (6.). PHI.
Lua i Stíl Chicago (17ú heag.)Tull, Donald S & Hawkins Del I. Marketing Research: Measurment & Method. 6. New delhi: PHI, 1960.
Lua MLA (9ú heag.)Tull, Donald S & Hawkins Del I. Marketing Research: Measurment & Method. 6. PHI, 1960.
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