APA استشهاد

Knorr, K., & Verba, S. (1961). The international system: Theoretical essays. Princeton university press.

استشهاد بنمط شيكاغو

Knorr, Klaus, و Sidney Verba. The International System: Theoretical Essays. USA: Princeton university press, 1961.

MLA استشهاد

Knorr, Klaus, و Sidney Verba. The International System: Theoretical Essays. Princeton university press, 1961.