People usually say "European Style", "Yan Style", "Liu Style" and "Zhao Ti" are named after the surnames of calligraphers Ou Yangxun, Yan Zhenqing, Liu Gongquan and Zhao Mengfu in the Yuan Dynasty.
"Four masters of regular script" refers to Ou Yangxun in the early Tang Dynasty, Yan Zhenqing in the prosperous Tang Dynasty, Liu Gongquan in the late Tang Dynasty and Zhao Mengfu in the Yuan Dynasty.