MLA

Fitzgerald, Robert, 1910-1985. Lindsay, Vachel. Box 24, folder 873. 1930-31. https://collections.library.yale.edu/catalog/17093651.

APA, 6th edition

Fitzgerald, Robert, 1910-1985. (["Box 24, folder 873"])(1930-31)[Lindsay, Vachel]. https://collections.library.yale.edu/catalog/17093651.