MLA

Saarinen, Eero, 1910-1961. Chair prototypes. Box 83, folder 156. undated. https://collections.library.yale.edu/catalog/10017290.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 83, folder 156"])(undated)[Chair prototypes]. https://collections.library.yale.edu/catalog/10017290.