MLA

Speck, William A. (William Alfred), 1864-1928. Offene Gegend. Box 7, folder 224. n.d.. https://collections.library.yale.edu/catalog/2005284.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 7, folder 224"])(n.d.)[Offene Gegend]. https://collections.library.yale.edu/catalog/2005284.