MLA

Saarinen, Eero, 1910-1961. Segovia. Box 12, folder 197. undated. https://collections.library.yale.edu/catalog/10020358.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 12, folder 197"])(undated)[Segovia]. https://collections.library.yale.edu/catalog/10020358.