MLA

Agnes Ledgerwood Hately, Edinburgh, Scotland, Letter to James Kinnier Wilson, Philadelphia, Pennsylvania. 1873. https://collections.library.yale.edu/catalog/16719860.

APA, 6th edition

Agnes Ledgerwood Hately, Edinburgh, Scotland, letter to James Kinnier Wilson, Philadelphia, Pennsylvania. (1873). [Correspondence, Manuscripts]. https://collections.library.yale.edu/catalog/16719860.