APA
Cornin A. J., Hopkins A., Potter J. & Wymer N. (2008). The Citadel. London: Penguin books ltd.
Chicago
Cornin A J, Hopkins Andy, Potter Jocelyn and Wymer Norman. 2008. The Citadel. London: Penguin books ltd.
Harvard
Cornin A. J., Hopkins A., Potter J. and Wymer N. (2008). The Citadel. London: Penguin books ltd.
MLA
Cornin A J, Hopkins Andy, Potter Jocelyn and Wymer Norman. The Citadel. London: Penguin books ltd. 2008.