MLA

Henri, Robert, 1865-1929. Notebook with notes on easels and canvas carriers and bylaws for an unidentified art society. Box 26, folder 610. n.d.. https://collections.library.yale.edu/catalog/17029601.

APA, 6th edition

Henri, Robert, 1865-1929. (["Box 26, folder 610"])(n.d.)[Notebook with notes on easels and canvas carriers and bylaws for an unidentified art society]. https://collections.library.yale.edu/catalog/17029601.