MLA

Pratt, Richard Henry, 1840-1924. Armstrong, Samuel C., 17 items. Box 1, folder 12. 1879. https://collections.library.yale.edu/catalog/16701072.

APA, 6th edition

Pratt, Richard Henry, 1840-1924. (["Box 1, folder 12"])(1879)[Armstrong, Samuel C., 17 items]. https://collections.library.yale.edu/catalog/16701072.