MLA

Barrie, J. M. (James Matthew), 1860-1937. Irving, Peter. Box 9, folder 270. 1875–1877. https://collections.library.yale.edu/catalog/17328108.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 9, folder 270"])(1875–1877)[Irving, Peter]. https://collections.library.yale.edu/catalog/17328108.