APA
Krugman P. R., Obstfeld M., Melitz M. J. & Krugman P. R. (2018). International Trade. New York, NY: Pearson Education.
Chicago
Krugman Paul R, Obstfeld Maurice, Melitz Marc J and Krugman Paul R. 2018. International Trade. New York, NY: Pearson Education.
Harvard
Krugman P. R., Obstfeld M., Melitz M. J. and Krugman P. R. (2018). International Trade. New York, NY: Pearson Education.
MLA
Krugman Paul R, Obstfeld Maurice, Melitz Marc J and Krugman Paul R. International Trade. New York, NY: Pearson Education. 2018.