MLA

Serge, Victor, 1890-1947. Gorkin, Julián. "Carta abierta à Julio Alvarez del Vayo," typescript carbon (2 copies). Box 14, folder 584. 1942 Apr 1. https://collections.library.yale.edu/catalog/17455300.

APA, 6th edition

Serge, Victor, 1890-1947. (["Box 14, folder 584"])(1942 Apr 1)[Gorkin, Julián. "Carta abierta à Julio Alvarez del Vayo," typescript carbon (2 copies)]. https://collections.library.yale.edu/catalog/17455300.