MLA

Saarinen, Eero, 1910-1961. Additional material. Box 672, folder 33. 1960, undated. https://collections.library.yale.edu/catalog/10016971.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 672, folder 33"])(1960, undated)[Additional material]. https://collections.library.yale.edu/catalog/10016971.