MLA

Kissinger, Henry, 1923-2023. Preface. Box 142, folder 7. Undated, circa 1956-circa 1958. https://collections.library.yale.edu/catalog/11784846.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 142, folder 7"])(Undated, circa 1956-circa 1958)[Preface]. https://collections.library.yale.edu/catalog/11784846.