MLA

Speck, William A. (William Alfred), 1864-1928. Two ink sketches. Box 3, folder 29. undated. https://collections.library.yale.edu/catalog/33390883.

APA, 6th edition

Speck, William A. (William Alfred), 1864-1928. (["Box 3, folder 29"])(undated)[Two ink sketches]. https://collections.library.yale.edu/catalog/33390883.