MLA

Thayer, Scofield, 1889-1982. Erdberg, Amy von. Box 1, folder 3. 1927. https://collections.library.yale.edu/catalog/10102220.

APA, 6th edition

Thayer, Scofield, 1889-1982. (["Box 1, folder 3"])(1927)[Erdberg, Amy von]. https://collections.library.yale.edu/catalog/10102220.