 Among them are a 14th-century Quran with beautiful calligraphy in Kufic script, writings of Avicenna (Ibn Sina), Ibn Rushd (Averroes), El Khwarizmi, a translation of Pythagoras, treatises on theology, astronomy, geography and pharmacology.Later sheikhs of the Sufi brotherhood of the Nasiriyya also played an important role as religious and cultural leaders and teachers of the Sufi doctrine (Tasawwuf).The 19th sheikh Abu Bekr is well-known, in the Draa valley (zawiya in Mhamid Ghuslan) and in the west through his encounters with the travelers Gerhard Rohlfs  and Charles de Foucauld.