MLA

Speck, William A. (William Alfred), 1864-1928. ALS, to Johann Wolfgang von Goethe. Box 11, folder 370. 1798 Jan 3. https://collections.library.yale.edu/catalog/2005378.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 11, folder 370"])(1798 Jan 3)[ALS, to Johann Wolfgang von Goethe]. https://collections.library.yale.edu/catalog/2005378.