APA (7th ed.) Citation

Seward, W. H., Barton, W. E., & William E. Barton Collection of Lincolniana. (1843). Autograph letter signed: Auburn, N.Y., to H.C. Van Schaick, n.p.

Chicago Style (17th ed.) Citation

Seward, William H., William E. Barton, and William E. Barton Collection of Lincolniana. Autograph Letter Signed: Auburn, N.Y., to H.C. Van Schaick, N.p. 1843.

MLA (8th ed.) Citation

Seward, William H., et al. Autograph Letter Signed: Auburn, N.Y., to H.C. Van Schaick, N.p. 1843.