MLA

Stevens, Isaac Ingalls, 1818-1862. Letter to Evans. Monday 12 [May 1856]. 2 p. Drafts of three letters from Gibbs and Goldsborough to the Secretary of State, William L. Marcy. May [11]-Jun [6] 1856. 22 p.. Box 1, folder 6. 1856. https://collections.library.yale.edu/catalog/17234238.

APA, 6th edition

Stevens, Isaac Ingalls, 1818-1862. (["Box 1, folder 6"])(1856)[Letter to Evans. Monday 12 [May 1856]. 2 p. Drafts of three letters from Gibbs and Goldsborough to the Secretary of State, William L. Marcy. May [11]-Jun [6] 1856. 22 p.]. https://collections.library.yale.edu/catalog/17234238.