MLA

Barrie, J. M. (James Matthew), 1860-1937. Llewelyn Davies, Michael. Box 10, folder 307. 1905–1921. https://collections.library.yale.edu/catalog/2008291.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 10, folder 307"])(1905–1921)[Llewelyn Davies, Michael]. https://collections.library.yale.edu/catalog/2008291.