MLA

Cassirer, Ernst, 1874-1945. Cohen, Hermann. Box 2, folder 33-34. 1901-29. https://collections.library.yale.edu/catalog/17289604.

APA, 6th edition

Cassirer, Ernst, 1874-1945. (["Box 2, folder 33-34"])(1901-29)[Cohen, Hermann]. https://collections.library.yale.edu/catalog/17289604.