MLA

Backus, Isaac, 1724-1806. Collected papers. box 8, folder 28. 1768 May–1768 July. https://collections.library.yale.edu/catalog/33555841.

APA, 6th edition

Backus, Isaac, 1724-1806. (["box 8, folder 28"])(1768 May–1768 July)[Collected papers]. https://collections.library.yale.edu/catalog/33555841.