MLA

Thayer, Scofield, 1889-1982. Freud, Sigmund. Box 32, folder 860. 1921-25, n.d.. https://collections.library.yale.edu/catalog/2110509.

APA, 6th edition

Thayer, Scofield, 1889-1982. (["Box 32, folder 860"])(1921-25, n.d.)[Freud, Sigmund]. https://collections.library.yale.edu/catalog/2110509.