The letters of Mark Twain and Joseph Hopkins Twichell

Twain, Mark, 1835-1910, author.
Athens, Georgia : The University of Georgia, [2017]

Mark Twain and Bret Harte.

Duckett, Margaret.
Norman : University of Oklahoma Press, [1964]

Mark Twain and male friendship : the Twichell, Howells, and Rogers friendships

Messent, Peter, 1946-
Oxford ; New York : Oxford University Press, 2009.

Twain in his own time : a biographical chronicle of his life, drawn from recollections, interviews,

Iowa City : University of Iowa Press, [2010]

Was Huck Black? : Mark Twain and African-American voices

Fishkin, Shelley Fisher.
New York : Oxford University Press, 1993.