MLA

MacDonald, George, 1824-1905. Matthews, Elizabeth. Box 2, folder 106. 1872 May 4. https://collections.library.yale.edu/catalog/16474499.

APA, 6th edition

MacDonald, George, 1824-1905. (["Box 2, folder 106"])(1872 May 4)[Matthews, Elizabeth]. https://collections.library.yale.edu/catalog/16474499.