MLA

Barrie, J. M. (James Matthew), 1860-1937. "Pirate Ship". Box 44, folder 947. undated. https://collections.library.yale.edu/catalog/32314844.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 44, folder 947"])(undated)["Pirate Ship"]. https://collections.library.yale.edu/catalog/32314844.