MLA

Kissinger, Henry, 1923-2023. Messages received, P. Box 150, folder 1. 1968-1973. https://collections.library.yale.edu/catalog/12479735.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 150, folder 1"])(1968-1973)[Messages received, P]. https://collections.library.yale.edu/catalog/12479735.