MLA

Kissinger, Henry, 1923-2023. Arno, Paula. Box 160, folder 21. 1960 May-June. https://collections.library.yale.edu/catalog/11785187.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 160, folder 21"])(1960 May-June)[Arno, Paula]. https://collections.library.yale.edu/catalog/11785187.