"An After-thought"
MLA
Barrie, J. M. (James Matthew), 1860-1937. "An After-thought". Box 43, folder 928. 1908. https://collections.library.yale.edu/catalog/32314353.
APA, 6th edition
Barrie, J. M. (James Matthew), 1860-1937. (["Box 43, folder 928"])(1908)["An After-thought"]. https://collections.library.yale.edu/catalog/32314353.