APA (7th ed.) Citation

Lincoln, M. T., Barton, W. E., & William E. Barton Collection of Lincolniana. (1866). Letter: Chicago, to Lucy A. Little, West Milton, Wis.

Chicago Style (17th ed.) Citation

Lincoln, Mary Todd, William E. Barton, and William E. Barton Collection of Lincolniana. Letter: Chicago, to Lucy A. Little, West Milton, Wis. 1866.

MLA (8th ed.) Citation

Lincoln, Mary Todd, et al. Letter: Chicago, to Lucy A. Little, West Milton, Wis. 1866.