MLA

Williams, William Carlos, 1883-1963. William George Williams. Box 71, folder 1485. circa 1880, 1858. https://collections.library.yale.edu/catalog/2044293.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 71, folder 1485"])(circa 1880, 1858)[William George Williams]. https://collections.library.yale.edu/catalog/2044293.