APA-referens (7:e uppl.)

Clemens, S. L., Howells, W. D., Smith, H. N. e., & Gibson, W. M. 1. . . e. (1960). Mark Twain-Howells letters: The correspondence of Samuel L. Clemens and William D. Howells, 1872-1910. Belknap Press of Harvard University Press.

Chicago-referens (17:e uppl.)

Clemens, Samuel Langhorne, William Dean Howells, Henry Nash ed Smith, och William Merriam 1912- ed Gibson. Mark Twain-Howells Letters: The Correspondence of Samuel L. Clemens and William D. Howells, 1872-1910. Cambridge: Belknap Press of Harvard University Press, 1960.

MLA-referens (9:e uppl.)

Clemens, Samuel Langhorne, et al. Mark Twain-Howells Letters: The Correspondence of Samuel L. Clemens and William D. Howells, 1872-1910. Belknap Press of Harvard University Press, 1960.