MLA

Wilfred, Thomas, 1889-1968. Miscellaneous. Box 15, folder 209. Undated. https://collections.library.yale.edu/catalog/10015545.

APA, 6th edition

Wilfred, Thomas, 1889-1968. (["Box 15, folder 209"])(Undated)[Miscellaneous]. https://collections.library.yale.edu/catalog/10015545.