Yehudai Gaon's Halachot Pesukot, Achai Gaon's Sheeltot and Simeon Kayyara's Halachot Gedolot. After the death of Hai Gaon, however, the center of Talmud scholarship shifts to Europe and North Africa. Halakhic and Aggadic extractions One area of Talmudic scholarship developed out of the need to ascertain the Halakha. Early commentators such as rabbi Isaac Alfasi (North Africa, 1013–1103) attempted to extract and determine the binding legal opinions from the vast corpus of the Talmud. Alfasi's work was highly influential, attracted several commentaries in its own right and later served as a basis for the creation of halakhic codes. Another influential medieval Halakhic work following the order of the Babylonian Talmud, and to some extent modelled on Alfasi, was "the Mordechai", a compilation by Mordechai ben Hillel ( 1250–1298). A third such work was that of rabbi Asher ben Yechiel (d. 1327). All these works and their commentaries are printed in the Vilna and many subsequent editions of the Talmud. A 15th-century Spanish rabbi, Jacob ibn Habib (d. 1516), composed the Ein Yaakov. Ein Yaakov (or En Ya'aqob) extracts nearly all the Aggadic material from the Talmud. It was intended to familiarize the public with the ethical parts of the Talmud and to dispute many of the accusations surrounding its contents. Commentaries The commentaries on the Talmud constitute only a small part of Rabbinic literature in comparison with the responsa literature and the commentaries on the codices. When the Talmud was concluded the traditional literature was still so fresh in the memory of scholars that no need existed for writing Talmudic commentaries, nor were such works undertaken in the first period of the gaonate. Paltoi ben Abaye (c. 840) was the first who in his responsum offered verbal and textual comments on the Talmud. His son, Zemah ben Paltoi paraphrased and explained the passages which he quoted; and he composed, as an aid to the study of the Talmud, a lexicon which Abraham Zacuto consulted in the fifteenth century. Saadia Gaon is said to have composed commentaries on the Talmud, aside from his Arabic commentaries on the Mishnah. There are many passages in the Talmud which are cryptic and difficult to understand. Its language contains many Greek and Persian words that became obscure over time. A major area of Talmudic scholarship developed to explain these passages and words. Some early commentators such as Rabbenu Gershom of Mainz (10th century) and Rabbenu