MLA

Saarinen, Eero, 1910-1961. "Grasshopper" chair. Box 83, folder 157. undated. https://collections.library.yale.edu/catalog/10015781.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 83, folder 157"])(undated)["Grasshopper" chair]. https://collections.library.yale.edu/catalog/10015781.