José Antonio Mayoral (2001). Thomas O Sloane. red (på engelska). Encyclopedia of Rhetoric. Oxford: Oxford University Press. sid. 89. LibrisOxford. ISBN 0-19-512595-9
Theresa Enos, red (1996) (på engelska). Encyclopedia of rhetoric and composition : communication from ancient times to the information age. New York: Garland Publ. sid. 100. LibrisYork New York. ISBN 0-8240-7200-6
Lennart Hellspong (2004). Konsten att tala. Handbok i praktisk retorik (2). Lund: Studentlitteratur. sid. 147. Libris9696836. ISBN 9144036345