Tolong jelaskan mengenai Sumber kedua dari Pertempuran Chester

Koch, John T. (2006). "Caer (Chester), Battle of". In Koch, John T. (ed.). Celtic Culture: A Historical Encyclopedia. Santa Barbara, Denver, and Oxford: ABC-CLIO. pp. 317–9.

Morris, John (1973). The Age of Arthur. Weidenfeld & Nicolson.