MLA

MacDonald, George, 1824-1905. "A" general. Box 1, folder 40. 1870, n.d.. https://collections.library.yale.edu/catalog/17297712.

APA, 6th edition

MacDonald, George, 1824-1905. (["Box 1, folder 40"])(1870, n.d.)["A" general]. https://collections.library.yale.edu/catalog/17297712.