APA (7th ed.) Citation

Harper Collins, Krugman, P. R., & Obstfeld, M. (1991). International economics: Theory and policy. Harper Collins.

Chicago Style (17th ed.) Citation

Harper Collins, Paul R. Krugman, and Maurice Obstfeld. International Economics: Theory and Policy. New York: Harper Collins, 1991.

MLA (8th ed.) Citation

Harper Collins, et al. International Economics: Theory and Policy. Harper Collins, 1991.