MLA

Johnson, James Weldon, 1871-1938. Brown, Sterling Allen. Box 4, folder 66. 1930-37, undated. https://collections.library.yale.edu/catalog/32459800.

APA, 6th edition

Johnson, James Weldon, 1871-1938. (["Box 4, folder 66"])(1930-37, undated)[Brown, Sterling Allen]. https://collections.library.yale.edu/catalog/32459800.