MLA

Kissinger, Henry, 1923-2023. Altenstetter, Christa. Box 2, folder 9. 1968. https://collections.library.yale.edu/catalog/11782308.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 2, folder 9"])(1968)[Altenstetter, Christa]. https://collections.library.yale.edu/catalog/11782308.