Xu Shen
The first known character dictionary was the 3rd century BC "Erya", collated and referenced by Liu Xiang and his son Liu Xin. It is no longer extant. Not long after, the "Shuowen Jiezi" (AD 100–121), the lifework of Xu Shen, was written. Its 9,353 entries reproduce the standardized small-seal script variant for each entry, and for some entries other pre-Han variants from the late Zhou era. Entries are categorized under 540 section headers.