MLA

Kissinger, Henry, 1923-2023. Essay on Albert Einstein for "100 Most Important People of the 19th Century," Time, Sep 27, 1999. Box 736, folder 2. 1999. https://collections.library.yale.edu/catalog/11781979.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 736, folder 2"])(1999)[Essay on Albert Einstein for "100 Most Important People of the 19th Century," Time, Sep 27, 1999]. https://collections.library.yale.edu/catalog/11781979.