Gaya APA
Cooper, D, R., Emory, C, W. (1991).
Business Research Methods (Edisi 4).
United States of Amerika:
Irwin Inc..
Gaya MLA
Cooper, Donald, R.., Emory, C., William.
"Business Research Methods".
Edisi 4
United States of Amerika:
Irwin Inc.,
1991.
.