MLA

Speck, William A. (William Alfred), 1864-1928. ALS : Teplitz, to Ernst Carl Christian John. Box 9, folder 283. 1813 Aug 9. https://collections.library.yale.edu/catalog/2005313.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 9, folder 283"])(1813 Aug 9)[ALS : Teplitz, to Ernst Carl Christian John]. https://collections.library.yale.edu/catalog/2005313.