MLA

Saarinen, Eero, 1910-1961. Additional material. Box 673, folder 57. 1961-1966, undated. https://collections.library.yale.edu/catalog/10021549.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 673, folder 57"])(1961-1966, undated)[Additional material]. https://collections.library.yale.edu/catalog/10021549.