MLA

Kissinger, Henry, 1923-2023. Gradl, Johann Baptist. Box 25, folder 18. 1959-1966. https://collections.library.yale.edu/catalog/11782777.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 25, folder 18"])(1959-1966)[Gradl, Johann Baptist]. https://collections.library.yale.edu/catalog/11782777.