MLA

Backus, Isaac, 1724-1806. The kingdom of God, described by His Word with infinite benefits to human society (ms. fragment). Box 5, folder 2. Undated. https://collections.library.yale.edu/catalog/33530762.

APA, 6th edition

Backus, Isaac, 1724-1806. (["Box 5, folder 2"])(Undated)[The kingdom of God, described by His Word with infinite benefits to human society (ms. fragment)]. https://collections.library.yale.edu/catalog/33530762.