MLA

Acton, Harold, 1904-1994. Act X. Listening to Music. Box 1, folder 83. 1933 1941. https://collections.library.yale.edu/catalog/16604555.

APA, 6th edition

Acton, Harold, 1904-1994. (["Box 1, folder 83"])(1933 1941)[Act X. Listening to Music]. https://collections.library.yale.edu/catalog/16604555.