MLA

Kissinger, Henry, 1923-2023. Fabregat, E. Rodríguez. Box 99, folder 4. 1961 September. https://collections.library.yale.edu/catalog/11784106.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 99, folder 4"])(1961 September)[Fabregat, E. Rodríguez]. https://collections.library.yale.edu/catalog/11784106.