MLA

Kissinger, Henry, 1923-2023. Young, Elizabeth. Box 324, folder 15. 1969. https://collections.library.yale.edu/catalog/11774859.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 324, folder 15"])(1969)[Young, Elizabeth]. https://collections.library.yale.edu/catalog/11774859.