MLA

Speck, William A. (William Alfred), 1864-1928. ALS : Jena, to Johann Wolfgang von Goethe. Box 5, folder 191. 1830 Feb 5. https://collections.library.yale.edu/catalog/2005270.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 5, folder 191"])(1830 Feb 5)[ALS : Jena, to Johann Wolfgang von Goethe]. https://collections.library.yale.edu/catalog/2005270.