APA (7th ed.) Citation

Krugman, P., Wells, R., & Olney, M. L. (2007). Essentials of economics. Worth Publ.

Chicago Style (17th ed.) Citation

Krugman, Paul, Robin Wells, and Martha L. Olney. Essentials of Economics. New York, NY: Worth Publ, 2007.

MLA (9th ed.) Citation

Krugman, Paul, et al. Essentials of Economics. Worth Publ, 2007.