Townshend, Charles (1 January 2000). The Oxford History of Modern War. Oxford University Press. p. 112. ISBN978-0-19-285373-8. Retrieved 4 January 2017 – via Internet Archive. acquired ravelins and redoubts, bonnettes and lunettes.
castlesandmanorhouses.com
"Star Forts". Types of Castle and The History of Castles. Castle and Manor Houses Resources. Retrieved 4 January 2017.