MLA

Brown, Ella Barksdale, 1871-1966. Event Flyers. Box 5, folder 135. 1909-1920. https://collections.library.yale.edu/catalog/2107159.

APA, 6th edition

Brown, Ella Barksdale, 1871-1966. (["Box 5, folder 135"])(1909-1920)[Event Flyers]. https://collections.library.yale.edu/catalog/2107159.