MLA

Barrie, J. M. (James Matthew), 1860-1937. Bandelero the Bandit. Box 32, folder 804. 1877 February 12. https://collections.library.yale.edu/catalog/10086144.

APA, 6th edition

Barrie, J. M. (James Matthew), 1860-1937. (["Box 32, folder 804"])(1877 February 12)[Bandelero the Bandit]. https://collections.library.yale.edu/catalog/10086144.