MLA

Newell, Peter, 1862-1924. McCormick, Frederick. Box 210, folder 2768. 1897. https://collections.library.yale.edu/catalog/17181132.

APA, 6th edition

Newell, Peter, 1862-1924. (["Box 210, folder 2768"])(1897)[McCormick, Frederick]. https://collections.library.yale.edu/catalog/17181132.