MLA

Acton, Harold, 1904-1994. Prefatory note by Harold Acton. Box 1, folder 2. 1933 1941. https://collections.library.yale.edu/catalog/16604500.

APA, 6th edition

Acton, Harold, 1904-1994. (["Box 1, folder 2"])(1933 1941)[Prefatory note by Harold Acton]. https://collections.library.yale.edu/catalog/16604500.