MLA

Saarinen, Eero, 1910-1961. Courtyard interiors. Box 228, folder 750. undated. https://collections.library.yale.edu/catalog/10012612.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 228, folder 750"])(undated)[Courtyard interiors]. https://collections.library.yale.edu/catalog/10012612.