MLA

Thayer, Scofield, 1889-1982. Hofmannsthal, Hugo von. Box 3, folder 96. 1924-29, n.d.. https://collections.library.yale.edu/catalog/17142281.

APA, 6th edition

Thayer, Scofield, 1889-1982. (["Box 3, folder 96"])(1924-29, n.d.)[Hofmannsthal, Hugo von]. https://collections.library.yale.edu/catalog/17142281.