MLA

Lewis, W. S. (Wilmarth Sheldon), 1895-1979. "Pensées philosophique". Box 9, folder 21. [1700s]. https://collections.library.yale.edu/catalog/33194368.

APA, 6th edition

Lewis, W. S. (Wilmarth Sheldon), 1895-1979. (["Box 9, folder 21"])([1700s])["Pensées philosophique"]. https://collections.library.yale.edu/catalog/33194368.