MLA

Thomson, Virgil, 1896-1989. Jackson, George Pullen. Box 29/54, folder 18. 1937-1956. https://collections.library.yale.edu/catalog/32233164.

APA, 6th edition

Thomson, Virgil, 1896-1989. (["Box 29/54, folder 18"])(1937-1956)[Jackson, George Pullen]. https://collections.library.yale.edu/catalog/32233164.