MLA

Barrie, J. M. (James Matthew), 1860-1937. Granville-Barker, Helen. Box 8, folder 213. 1927–1936. https://collections.library.yale.edu/catalog/17328107.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 8, folder 213"])(1927–1936)[Granville-Barker, Helen]. https://collections.library.yale.edu/catalog/17328107.