MLA

Wilder, Thornton, 1897-1975. University of Texas at Austin. Box 60, folder 1666. 1960-64. https://collections.library.yale.edu/catalog/32267342.

APA, 6th edition

Wilder, Thornton, 1897-1975. (["Box 60, folder 1666"])(1960-64)[University of Texas at Austin]. https://collections.library.yale.edu/catalog/32267342.