SEKARAN UMA. (1992). RESEARCH METHODS FOR BUSINESS: A SKILL-BUILDING APPROACH (2ND.). JOHN WILEY AND SONS.
Lua i Stíl Chicago (17ú heag.)SEKARAN UMA. RESEARCH METHODS FOR BUSINESS: A SKILL-BUILDING APPROACH. 2ND. NEW YORK: JOHN WILEY AND SONS, 1992.
Lua MLA (9ú heag.)SEKARAN UMA. RESEARCH METHODS FOR BUSINESS: A SKILL-BUILDING APPROACH. 2ND. JOHN WILEY AND SONS, 1992.
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