MLA

Luhan, Mabel Dodge, 1879-1962. Jeffers, Robinson. Box 72, folder 1978. 1929-39, n.d.. https://collections.library.yale.edu/catalog/16789828.

APA, 6th edition

Luhan, Mabel Dodge, 1879-1962. (["Box 72, folder 1978"])(1929-39, n.d.)[Jeffers, Robinson]. https://collections.library.yale.edu/catalog/16789828.