MLA

Clark, William, 1770-1838. Route about October 20-21, 1805, and return camps for April 21, 22, 23, and 24, 1806. Box 2, folder 40. circa 1803-1810. https://collections.library.yale.edu/catalog/2002488.

APA, 6th edition

Clark, William, 1770-1838. (["Box 2, folder 40"])(circa 1803-1810)[Route about October 20-21, 1805, and return camps for April 21, 22, 23, and 24, 1806]. https://collections.library.yale.edu/catalog/2002488.