MLA

Newell, Peter, 1862-1924. McCormick, Frederick. Box 214, folder 2893. 1929-63. https://collections.library.yale.edu/catalog/17181133.

APA, 6th edition

Newell, Peter, 1862-1924. (["Box 214, folder 2893"])(1929-63)[McCormick, Frederick]. https://collections.library.yale.edu/catalog/17181133.