MLA

Adams, Léonie, 1899-1988. Chapin, Katherine Garrison. Box 1, folder 61. 1950-1971, undated. https://collections.library.yale.edu/catalog/17204537.

APA, 6th edition

Adams, Léonie, 1899-1988. (["Box 1, folder 61"])(1950-1971, undated)[Chapin, Katherine Garrison]. https://collections.library.yale.edu/catalog/17204537.