MLA

Steinberg, Saul, 1914-1999. Lattuda, Alberto. Box 26, folder 482. 1946-1993, undated. https://collections.library.yale.edu/catalog/10034222.

APA, 6th edition

Steinberg, Saul, 1914-1999. (["Box 26, folder 482"])(1946-1993, undated)[Lattuda, Alberto]. https://collections.library.yale.edu/catalog/10034222.