MLA

Kissinger, Henry, 1923-2023. "NATO's Future after Enlargement," Polish-German-American Forum for Security, Warsaw, Dec 6, 1997. Box 731, folder 4. 1997. https://collections.library.yale.edu/catalog/11781910.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 731, folder 4"])(1997)["NATO's Future after Enlargement," Polish-German-American Forum for Security, Warsaw, Dec 6, 1997]. https://collections.library.yale.edu/catalog/11781910.