MLA

Steinberg, Saul, 1914-1999. "C" General. Box 8, folder 142-143 | Box 9, folder 144-153 | Box 10, folder 154-158 | Box 500 (Oversize), folder 6981. 1942-1998, undated. https://collections.library.yale.edu/catalog/2067993.

APA, 6th edition

Steinberg, Saul, 1914-1999. (["Box 8, folder 142-143 | Box 9, folder 144-153 | Box 10, folder 154-158 | Box 500 (Oversize), folder 6981"])(1942-1998, undated)["C" General]. https://collections.library.yale.edu/catalog/2067993.