MLA

Kissinger, Henry, 1923-2023. Ewell, Raymond. Box 199, folder 10. 1968 January. https://collections.library.yale.edu/catalog/11785829.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 199, folder 10"])(1968 January)[Ewell, Raymond]. https://collections.library.yale.edu/catalog/11785829.