Cita APA (7a ed.)

Ruffin, R. J., & Gregory, P. R. (1983). Principles of economics. Scott, Foresman and Company.

Cita Chicago Style (17a ed.)

Ruffin, Roy J., y Paul R. Gregory. Principles of Economics. Glenview, Illinois [etc.]: Scott, Foresman and Company, 1983.

Cita MLA (9a ed.)

Ruffin, Roy J., y Paul R. Gregory. Principles of Economics. Scott, Foresman and Company, 1983.