Magness, Phillip W. (Winter 2008). "Benjamin Butler's Colonization Testimony Reevaluated". Journal of the Abraham Lincoln Association. 29 (1). hdl:2027/spo.2629860.0029.103. ISSN1945-7987.
"The House Impeaches Andrew Johnson". Washington, D.C.: Office of the Historian and the Clerk of the House's Office of Art and Archives. Retrieved January 13, 2021.
Magness, Phillip W. (Winter 2008). "Benjamin Butler's Colonization Testimony Reevaluated". Journal of the Abraham Lincoln Association. 29 (1). hdl:2027/spo.2629860.0029.103. ISSN1945-7987.