MLA

Berssenbrugge, Mei-mei, 1947-. Ashbery, John. Box 1. 1992-2007, undated. https://collections.library.yale.edu/catalog/32236471.

APA, 6th edition

Berssenbrugge, Mei-mei, 1947-. (["Box 1"])(1992-2007, undated)[Ashbery, John]. https://collections.library.yale.edu/catalog/32236471.