Ball, D., & Ball, D. (2001). Bisnis International/Ball Donald, Wendell H. McCulloch. Salemba Empat.
Lua i Stíl Chicago (17ú heag.)Ball, Donald, agus Donald Ball. Bisnis International/Ball Donald, Wendell H. McCulloch. Salemba Empat, 2001.
Lua MLA (8ú heag.)Ball, Donald, agus Donald Ball. Bisnis International/Ball Donald, Wendell H. McCulloch. Salemba Empat, 2001.
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