MLA

Oenslager, Donald, 1902-1975. Terry, Ellen, printed version of letter from 9 November 1913. Box 1, folder 52. n.d.. https://collections.library.yale.edu/catalog/16538046.

APA, 6th edition

Oenslager, Donald, 1902-1975. (["Box 1, folder 52"])(n.d.)[Terry, Ellen, printed version of letter from 9 November 1913]. https://collections.library.yale.edu/catalog/16538046.