MLA

Wallace, Susan E. (Susan Elston), 1830-1907. Letter : Crawfordsville, Ind., to Helen Lossing and Mr. Lossing. Box 6, folder GROUP 105, F-1. 1870 Mar 22. https://collections.library.yale.edu/catalog/2014443.

APA, 6th edition

Wallace, Susan E. (Susan Elston), 1830-1907. (["Box 6, folder GROUP 105, F-1"])(1870 Mar 22)[Letter : Crawfordsville, Ind., to Helen Lossing and Mr. Lossing]. https://collections.library.yale.edu/catalog/2014443.