MLA

Backus, Isaac, 1724-1806. Collected papers. box 9, folder 23. 1771 December. https://collections.library.yale.edu/catalog/33576600.

APA, 6th edition

Backus, Isaac, 1724-1806. (["box 9, folder 23"])(1771 December)[Collected papers]. https://collections.library.yale.edu/catalog/33576600.