MLA

Clark, William, 1770-1838, Lewis, Meriwether, 1774-180. Route about September 18-October 7, 1805. Box 1 | Folder 35. 1805?. https://collections.library.yale.edu/catalog/2002483.

APA, 6th edition

Clark, William, 1770-1838, & Lewis, Meriwether, 1774-180. (["Box 1 | Folder 35"])(1805?)[Route about September 18-October 7, 1805]. https://collections.library.yale.edu/catalog/2002483.