MLA

Lewis, Sinclair, 1885-1951. Rowolt Verlag. Box 48, folder 598. 1933-1946. https://collections.library.yale.edu/catalog/17116549.

APA, 6th edition

Lewis, Sinclair, 1885-1951. (["Box 48, folder 598"])(1933-1946)[Rowolt Verlag]. https://collections.library.yale.edu/catalog/17116549.