MLA

Luhan, Mabel Dodge, 1879-1962. Momaday, Natachee [Scott?]. Box 26, folder 718. 1945 Oct 26. https://collections.library.yale.edu/catalog/17085360.

APA, 6th edition

Luhan, Mabel Dodge, 1879-1962. (["Box 26, folder 718"])(1945 Oct 26)[Momaday, Natachee [Scott?]]. https://collections.library.yale.edu/catalog/17085360.