MLA

Thayer, Scofield, 1889-1982. Schnitzler, Arthur. Box 57, folder 1529. n.d.. https://collections.library.yale.edu/catalog/10034096.

APA, 6th edition

Thayer, Scofield, 1889-1982. (["Box 57, folder 1529"])(n.d.)[Schnitzler, Arthur]. https://collections.library.yale.edu/catalog/10034096.