MLA

Byron, Robert, 1905-1941. Notebooks. Box 22, folder 430-435. undated. https://collections.library.yale.edu/catalog/2107220.

APA, 6th edition

Byron, Robert, 1905-1941. (["Box 22, folder 430-435"])(undated)[Notebooks]. https://collections.library.yale.edu/catalog/2107220.