MLA

Baldwin, James, 1924-1987. Letter : to Sam[uel L. Blumenfeld]. Box 1, folder GROUP 4, F-7. 1954 January 11. https://collections.library.yale.edu/catalog/16824874.

APA, 6th edition

Baldwin, James, 1924-1987. (["Box 1, folder GROUP 4, F-7"])(1954 January 11)[Letter : to Sam[uel L. Blumenfeld]]. https://collections.library.yale.edu/catalog/16824874.