MLA

Serge, Victor, 1890-1947. Cárdenas, Lázaro. Box 1, folder 12. 1942. https://collections.library.yale.edu/catalog/16495423.

APA, 6th edition

Serge, Victor, 1890-1947. (["Box 1, folder 12"])(1942)[Cárdenas, Lázaro]. https://collections.library.yale.edu/catalog/16495423.