^O'Connor, Thomas (2004). "Butler, John, styled twelfth Baron Dunboyne (1731–1800)". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/4196. Retrieved 2012-11-01. (Subscription or UK public library membership required.)
^Kidd, Charles; Williamson, David, eds. (1990). Debrett's Peerage and Baronetage. New York: St. Martin's Press.