APA (7th ed.) Citation

Olson, W. C., & Groom, A. J. R. (1991). International relations then and now: Origins and trends in interpretation. Routledge.

Chicago Style (17th ed.) Citation

Olson, William C., and A. J. R. Groom. International Relations Then and Now: Origins and Trends in Interpretation. London: Routledge, 1991.

MLA (9th ed.) Citation

Olson, William C., and A. J. R. Groom. International Relations Then and Now: Origins and Trends in Interpretation. Routledge, 1991.