Responsa are questions addressed to rabbinical authorities and their answers. In Hebrew they are called Sheeloth uTeshuboth. These letters were also called missives or adjudications, and they form part of rabbinical literature. Rabbis interpret the Bible and the Talmud and issue rulings in specific legal disputes. Responsa cover a wide spectrum of Jewish life, ranging from questions of everyday religious observance to ethical problems and scientific issues in mathematics, geography, and calendar systems. Responsa were first issued at the beginning of the 3rd century and are still issued today. The rulings contained in Responsa are a valuable source of information on local customs in particular Jewish communities, because rabbis often based their rulings on local custom and practice. They thus offer a rich picture of the social, economic, political and cultural situation of the Jews and their lifestyle where no other source of information is available. Questions and answers which recur throughout different centuries yield a a glimpse of the inner evolution of Judaism. Frankfurt rabbis also published famous Responsa: Chief Rabbi Ahron Samuel Kaidnower (also named Kojdanower) held office between 1667 and 1677, and describes the difficult situation of Jews in Germany. Jakob Hakohen Popers was chief rabbi in Frankfurt between 1717 and 1740 and left a major anthology of Responsa entitled "Shev Jakob", published in Frankfurt in 1742.