Gaya APA

Case, K, E., Oster, R, C, F, &, S, M. (2013). Principles of Economics (Tenth Edition). England: Pearson Education.

Gaya MLA

Case, Karl, E.., Oster, Ray, C., Fair, &, Sharon, M.. "Principles of Economics". Tenth Edition England: Pearson Education, 2013. Text.