MLA

Byron, Robert, 1905-1941. Weir, Thyra. Box 14, folder 336. 1930-1934, undated. https://collections.library.yale.edu/catalog/11676598.

APA, 6th edition

Byron, Robert, 1905-1941. (["Box 14, folder 336"])(1930-1934, undated)[Weir, Thyra]. https://collections.library.yale.edu/catalog/11676598.