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.
The latter was a prolific writer of great influence, chiefly known for his Responsa, but also for his halakhic treatiseE, hiddushin and tosaphot.h.
YAIR BACHARACH (1639-1702), German rabbi, was the author of Ilawwoth Yair (a collection of Responsa) and other works.
He was author of many "Responsa," but his chief work was liturgical.
Them; Pope Nicholas, however (858-867), in the Responsa ad consulta Bulgarorum, allowed baptism to be valid tantum in nomine Christi, as in the Acts.
He wrote glosses to the Talmud (tosaphot) and many Responsa of the utmost value for historical research.
He was also a Talmudist of high repute, and wrote glosses on various Tractates, Responsa and other legal works.