MLA

Backus, Isaac, 1724-1806. A seasonable plea for liberty of conscience, against some late oppressive proceedings; particularly in the town of Berwick, in the county of York. Box 5, folder 8. 1770. https://collections.library.yale.edu/catalog/33530905.

APA, 6th edition

Backus, Isaac, 1724-1806. (["Box 5, folder 8"])(1770)[A seasonable plea for liberty of conscience, against some late oppressive proceedings; particularly in the town of Berwick, in the county of York]. https://collections.library.yale.edu/catalog/33530905.