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 Nán-Tángshū biography. His monumental work, the Shuōwén xìzhuàn KR1j0019 in 40 juàn (the Xiǎo-Xúběn 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 Dà Xúběn 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.