MLA

Kissinger, Henry, 1923-2023. Bowie, Robert. Box 120, folder 21. 1957 August-1958 July. https://collections.library.yale.edu/catalog/11784457.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 120, folder 21"])(1957 August-1958 July)[Bowie, Robert]. https://collections.library.yale.edu/catalog/11784457.