MLA

Dean, L. E. R., and Lilly Dean. [Autograph Letter Signed] 1883 November 5, Tillamook County, Oregon [to] William Coates. 1883. https://collections.library.yale.edu/catalog/2054803.

APA, 6th edition

Dean, L. E. R., & Dean, L. (1883). [Autograph letter signed] 1883 November 5, Tillamook County, Oregon [to] William Coates [Autographs, Correspondence]. https://collections.library.yale.edu/catalog/2054803.