MLA

Kissinger, Henry, 1923-2023. Sorensen, Theodore. Box 55, folder 26. 1964-1968. https://collections.library.yale.edu/catalog/11783454.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 55, folder 26"])(1964-1968)[Sorensen, Theodore]. https://collections.library.yale.edu/catalog/11783454.