MLA

Backus, Isaac, 1724-1806. Reasons of my withdrawing communion with Paedobaptists, which I once stood with. Box 2, folder 4, item 2629214. 1756. https://collections.library.yale.edu/catalog/33499958.

APA, 6th edition

Backus, Isaac, 1724-1806. (["Box 2, folder 4, item 2629214"])(1756)[Reasons of my withdrawing communion with Paedobaptists, which I once stood with]. https://collections.library.yale.edu/catalog/33499958.