Individual Geonim produced valuable works (of which later), but what is perhaps most important from the point of view of the development of Judaism is the literature of their Responsa or answers to questions, chiefly on halakhic matters, addressed to them from various countries.
Besides the Responsa, but closely related to them, we have the lesser Halakhoth of Yehudai Gaon of Sura (8th century) and the great Halakhoth of Simeon Qayyara of Sura (not Gaon) in the 9th century.
(partly in Arabic) not only numerous Responsa, but also treatises on law, commentaries on the Mishnah and the Bible, a lexicon called in Arabic al-Hawi, and poems such as the Musar Haskel, but most of them are now lost or known only from translations or.
1141 at Lucena), a friend of Judah Ha-levi and of Moses ben Ezra, wrote Responsa and IIiddushin (annotations) on parts of the Talmud.
1171), the grandson of Rashi, wrote the Sepher ha-yashar (hiddushin and responsa) and was one of the chief Tosaphists.