Gaya APA
W, C, J. (2014).
Research Design:Qualitatived,Quantitative,& Mixed Methods Approaches .
California:
Sage Publications,Inc.
Gaya MLA
W, Creswel, John.
"Research Design:Qualitatived,Quantitative,& Mixed Methods Approaches".
California:
Sage Publications,Inc,
2014.
Text.