found: Institute of Ismaili Studies website, Oct. 17, 2018(Tayyibis; Musta'li Tayyibi Ismailis; a branch of the Shi'a Musta'li Ismailis; upon the death of the twentieth Imam of the Musta'li Ismailis, Fatimid Caliph al-'Amir bi-Ahkam Allah (d. 1130), the Musta'li community split into rival Hafizi and Tayyibi groups; the official Musta'li da'wa in Cairo recognised al 'Amir's cousin, al-Hafiz as the next Imam-Caliph (hence, Hafiziyya); in Yemen, the majority of Must'ali Ismailis along with some groups in Egypt and Syria upheld the rights of al-'Amir's infant son, al-Tayyib, as the rightful imam (hence, Tayyibiyya); the Tayyibis believe that the infant imam al-Tayyib went into concealment and, since then, the Musta'li Imamat in his line has continued in concealment; the centers of the Tayyibi community are in Yemen and India)