MLA

Steinberg, Saul, 1914-1999. Danson, Henrietta. Box 13, folder 228. 1943-1998, undated. https://collections.library.yale.edu/catalog/2067987.

APA, 6th edition

Steinberg, Saul, 1914-1999. (["Box 13, folder 228"])(1943-1998, undated)[Danson, Henrietta]. https://collections.library.yale.edu/catalog/2067987.