There are two books called Xu fangyan 續方言 "Supplement to the Fangyan".
The first was written by the Qing-period 清 (1644-1911) scholar Hang Shijun 杭世駿 (1696－1773). It is 2-juan long and constitutes a supplement to the Han-period 漢 (206 BCE-220 CE) topolect glossary dictionary Fangyan 方言 of Yang Xiong 揚雄 (53 BCE-18 CE). Hang collected quotations from the Confucian Classics and its commentaries, the dictionaries Shuowen jiezi 說文解字 and Shiming 釋名 to add 255 entries not listed in the Fanyang. The arrangement of the words follows the pattern in the Erya 爾雅 glossary. Yet there are still informations from Han period literature not included in Hang's Xu fangyan, while he also included words already provided in the old Fangyan.
At the end of Hang's Xu fangyan is a supplement which seems to have been added by someone else at a later date. It is included in the series Hangshi qizhong 杭氏七種 "Seven books of Master Hang", Yihai zhuchen 藝海珠塵, Zhaodai congshu 昭代叢書, and there is an edition from the Cungushu Studio 存古書局 in Chengdu, and a print from 1896, included in the collection Daogutang waiji 道古堂外集 of Wang Dajun 汪大鈞 (1862-1906).
The second book with the title Xu fangyan was compiled by the philosopher Dai Zhen 戴震 (1723-1777). It is only preserved as a personal manuscript written by Dai, which was reprinted as a facsimile in 1932. The sources of Dai were fare more numerous than those Hang Shijun had used, but also his collection of fragments covers not the total available range of Han-period literature and commentaries. The Dai Zhen version lists 22 entries more than the Hang Shijun version. It is included in the collected works of Dai, Dai Dongyuan xiansheng quanji 戴東原先生全集 in the series Anhui congshu 安徽叢書 from 1936.