Which four calligraphers in the Tang Dynasty are collectively called the Four Masters of the Early Tang Dynasty?

In terms of calligraphy: the four great masters of the early Tang Dynasty.

The "Four Great Masters of the Early Tang Dynasty" refers to the four calligraphers of the early Tang Dynasty: Ouyang Xun, Yu Shinan, Chu Suiliang, and Xue Ji. The top three are sometimes collectively known as the "Three Great Masters of the Early Tang Dynasty". The calligraphy of the four masters of the early Tang Dynasty has a unique feature, that is, the style of regular script is "delicate, thin and vigorous". Among them, Ouyang Xun's regular script is more prominent and has made the greatest contribution. It is merged with the later Yan Zhenqing, Liu Gongquan and Zhao Mengfu. Known as one of the "Four Masters of Regular Script", his "Jiucheng Palace" has always been regarded as a model for learning regular script. The later "thin gold body" can also be traced back to this. The main source of the thin gold body of Zhao Ji, Emperor Huizong of the Song Dynasty, was Xue Ji. However, it is impossible for any calligrapher to just copy or learn from one predecessor. They often specialize in one, learn from others, draw nourishment from the vast ocean of calligraphy, and eventually become their own.