MLA

Covarrubias, Miguel, 1904-1957. [Christmas cards]. Box 249 | Folder 2802. 1925, undated. https://collections.library.yale.edu/catalog/10000263.

APA, 6th edition

Covarrubias, Miguel, 1904-1957. (["Box 249 | Folder 2802"])(1925, undated)[[Christmas cards]]. https://collections.library.yale.edu/catalog/10000263.