New History of the Five Dynasties
The names and titles used by Southern Tang rulers changed several times throughout its existence. In the 930s Xu Zhigao ruled as king over a sizeable territory called Qi (齊) that existed within Wu. After deposing the Yang Imperial family in 937 he adopted the title of emperor and announced the creation Great Qi (大齊). The "Zizhi Tongjian" referred to this state as Tang from its foundation, while the majority of historical sources, including the "Old History of the Five Dynasties", "New History of the Five Dynasties", and the "Spring and Autumn Annals of the Ten Kingdoms", referred to the state as Qi. They begin to use Tang only after Xu Zhigao adopted the name Li Bian in 939.