MLA
Riddick, Elbert. Letter from Elbert Riddick to His Wife Lavina Riddick (Gatesville, North Carolina). Riddick Served in Company C of the 19th North Carolina Infantry Regiment - December 29, 1862 (Photcopy). 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 10, Folder 1. https://digital.library.emory.edu/purl/3246q574r2-cor.
APA, 6th edition
Riddick, E. (1862). Letter from Elbert Riddick to his wife Lavina Riddick (Gatesville, North Carolina). Riddick served in Company C of the 19th North Carolina Infantry Regiment - December 29, 1862 (photcopy) (Box 10, Folder 1) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3246q574r2-cor.
Chicago
Riddick, Elbert. “Letter from Elbert Riddick to His Wife Lavina Riddick (Gatesville, North Carolina). Riddick Served in Company C of the 19th North Carolina Infantry Regiment - December 29, 1862 (Photcopy).” Letters (correspondence). Civil War Collection, 1862. Box 10, Folder 1. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3246q574r2-cor.