MLA

Speck, William A. (William Alfred), 1864-1928. [Jery und Bätely. Singspiel in 1 Akt von Goethe]. Box 1, folder 14. n.d.. https://collections.library.yale.edu/catalog/2064618.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 1, folder 14"])(n.d.)[[Jery und Bätely. Singspiel in 1 Akt von Goethe]]. https://collections.library.yale.edu/catalog/2064618.