MLA

Lee, Richard C. (Richard Charles), 1916-2003. Conference with President Eisenhower and Powder House Day. Box 141, folder 2374. 1957 April. https://collections.library.yale.edu/catalog/10014764.

APA, 6th edition

Lee, Richard C. (Richard Charles), 1916-2003. (["Box 141, folder 2374"])(1957 April)[Conference with President Eisenhower and Powder House Day]. https://collections.library.yale.edu/catalog/10014764.