MLA

Johnson, A. B. (Alexander Bryan), 1786-1867. 1856, undated. Box 3, folder 20. 1856, undated. https://collections.library.yale.edu/catalog/32531197.

APA, 6th edition

Johnson, A. B. (Alexander Bryan), 1786-1867. (["Box 3, folder 20"])(1856, undated)[1856, undated]. https://collections.library.yale.edu/catalog/32531197.