Tài liệu tham khảo WikiPedia: Hạc_thành http://www.nguyenthaihocfoundation.org/lichsuVN/Th... http://wikimapia.org/8335651/vi/Th%C3%A0nh-c%E1%BB... https://noitraitim.wordpress.com/2012/08/06/truyen...