MLA

Kissinger, Henry, 1923-2023. Lehman, John. Box 427, folder 7. 1979 Dec, undated. https://collections.library.yale.edu/catalog/11777677.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 427, folder 7"])(1979 Dec, undated)[Lehman, John]. https://collections.library.yale.edu/catalog/11777677.