Southern-Táng scholar-official and philologist, zì Chǔjīn 楚金, of Guǎnglíng 廣陵 (modern Yangzhou). Younger brother of Xú Xuàn 徐鉉. Held high Southern-Táng office, rising to yòu nèishǐ shèrén 右內史舍人. He died in the besieged Southern-Táng capital Jīnlíng during the Sòng campaign of 974; his life is in the NánTángshū biography. His monumental work, the Shuōwén xìzhuàn KR1j0019 in 40 juàn (the XiǎoXúběn 小徐本 of Shuōwén studies), is the only deep philological commentary on the Shuōwén jiězì surviving from the medieval period and a precursor to the great Qing Shuōwén studies; it predates his elder brother’s DàXúběn recension. He also produced the Shuōwén jiězì zhuànyùnpǔ KR1j0021 — a phonologically-organized recasting of the Shuōwén lemmata. Several minor philological works of his survive in fragments. CBDB gives his death-year as 974 with fl. 943–960; the Sòngshǐ and the catalog meta both give 920–974, in agreement with the standard biographical sources.