APA (7th ed.) Citation
Ruffin, R. J., & Gregory, P. R. (1990). Principles of economics (4th ed.). Scott, Foresman.
Chicago Style (17th ed.) Citation
Ruffin, Roy J., and Paul R. Gregory. Principles of Economics. 4th ed. Glenview, Illinos: Scott, Foresman, 1990.
MLA (9th ed.) Citation
Ruffin, Roy J., and Paul R. Gregory. Principles of Economics. 4th ed. Scott, Foresman, 1990.
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