MLA

Barrie, J. M. (James Matthew), 1860-1937. Barrie and Michael Llewelyn Davies. Box 59, folder 1180. 1911. https://collections.library.yale.edu/catalog/2008270.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 59, folder 1180"])(1911)[Barrie and Michael Llewelyn Davies]. https://collections.library.yale.edu/catalog/2008270.