MLA
Wesley, Sarah, 1759-1828. Letter from Sarah Wesley to [Doctor] Tarpley "To be opened at my death", Chesterfield Street [London] - February, 1788. February 1788. Wesleyana Collection. Pitts Theology Library. https://digital.library.emory.edu/purl/904dncjtgf-cor.
APA, 6th edition
Wesley, Sarah, 1759-1828. (February 1788)[Letter from Sarah Wesley to [Doctor] Tarpley "To be opened at my death", Chesterfield Street [London] - February, 1788]. Wesleyana Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/904dncjtgf-cor.
Chicago
Wesley, Sarah, 1759-1828, Letter from Sarah Wesley to [Doctor] Tarpley "To be opened at my death", Chesterfield Street [London] - February, 1788, February 1788, Wesleyana Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/904dncjtgf-cor.