MLA

Brasol, Boris, 1885-. The Invisible Encounter Letter. Box 1 | Folder 7. 1943 November 16. https://collections.library.yale.edu/catalog/17351388.

APA, 6th edition

Brasol, Boris, 1885-. (["Box 1 | Folder 7"])(1943 November 16)[The Invisible Encounter Letter]. https://collections.library.yale.edu/catalog/17351388.