MLA

Luhan, Mabel Dodge, 1879-1962. Acton, Arthur. Box 1, folder 9-12. 1914-52, n.d.. https://collections.library.yale.edu/catalog/17085351.

APA, 6th edition

Luhan, Mabel Dodge, 1879-1962. (["Box 1, folder 9-12"])(1914-52, n.d.)[Acton, Arthur]. https://collections.library.yale.edu/catalog/17085351.