MLA

Saarinen, Eero, 1910-1961. Brochure for Knoll armchair and invitation to reception. Box 83, folder 146. 1957, undated. https://collections.library.yale.edu/catalog/10015865.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 83, folder 146"])(1957, undated)[Brochure for Knoll armchair and invitation to reception]. https://collections.library.yale.edu/catalog/10015865.