MLA

Backus, Isaac, 1724-1806. Collected papers. box 9, folder 30. 1772 September 4–1772 September 9. https://collections.library.yale.edu/catalog/33578701.

APA, 6th edition

Backus, Isaac, 1724-1806. (["box 9, folder 30"])(1772 September 4–1772 September 9)[Collected papers]. https://collections.library.yale.edu/catalog/33578701.