four famous Song calligraphers, namely: Su Shi 蘇軾|苏轼[Su1 Shi4], Huang Tingjian 黃庭堅|黄庭坚[Huang2 Ting2 jian1], Mi Fu 米芾[Mi3 Fu2] and Cai Xiang 蔡襄[Cai4 Xiang1]