1. 1. For a survey of modern knowledge about the Ka'ba, including the Muslim legends about its foundation, seeA.J. Wensinck, "Ka'ba ," Encyclopaedia of Islam, 1st and 2nd eds. (the latter with additions and deletions by J. Jomier).
2. On the notion of Mecca as the navel of the earth, seeA.J. Wensinck, "The Ideas of the Western Semites Concerning the Navel of the Earth" (Amsterdam; 1916 ),
3. 2. On the religious duty to face Mecca in prayer, seeA.J. Wensinck, "Kibla(ritual and legal aspects) ," Encyclopaedia of Islam, 2nd ed.
4. 3. A survey of medieval Islamicqibladeterminations by mathematical procedures is contained inD.A. King, "Kibla(astronomical aspects) ," Encyclopaedia of Islam, 2nd ed., which contains references to all the available published literature.