Donald Cooper. (2019). Business Reserarch Methods (12th ed.). McGraw Hill.
Lua i Stíl Chicago (17ú heag.)Donald Cooper. Business Reserarch Methods. 12th ed. Delhi: McGraw Hill, 2019.
Lua MLA (9ú heag.)Donald Cooper. Business Reserarch Methods. 12th ed. McGraw Hill, 2019.
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