MLA

Barrie, J. M. (James Matthew), 1860-1937. Autograph manuscript. Box 30, folder 791. circa 1889. https://collections.library.yale.edu/catalog/2008249.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 30, folder 791"])(circa 1889)[Autograph manuscript]. https://collections.library.yale.edu/catalog/2008249.