Cite

ALS : Cassel, to "Geehrter Freund"

MLA

Speck, William A. (William Alfred), 1864-1928. ALS : Cassel, to "Geehrter Freund". Box 16, folder 660. 1852 Apr 26. https://collections.library.yale.edu/catalog/17266946.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 16, folder 660"])(1852 Apr 26)[ALS : Cassel, to "Geehrter Freund"]. https://collections.library.yale.edu/catalog/17266946.