MLA

Newell, Peter, 1862-1924. Outgoing. Box 7, folder 100. 1879-80. https://collections.library.yale.edu/catalog/9998655.

APA, 6th edition

Newell, Peter, 1862-1924. (["Box 7, folder 100"])(1879-80)[Outgoing]. https://collections.library.yale.edu/catalog/9998655.