Four Great Calligraphers of early Tang; refers to Yu Shinan 虞世南[Yú​Shì​nán], Ouyang Xun 歐陽詢|欧阳询[Oū​yáng​Xún], Chu Suiliang 褚遂良[Chǔ​Suì​liáng] and Xue Ji 薛稷[Xuē​Jì]