The "dyula" have been predominantly Muslim since the 13th century. Many in rural areas combine Islamic beliefs with certain pre-Islamic animistic traditions such as the presence of spirits and use of amulets. "Dyula" communities have a reputation for historically maintaining a high standard of Muslim education. The "dyula" family enterprise based on the "lu" could afford to provide some of its younger men an Islamic education. Thus, an "ulema" (clerical) class known as karamogo emerged, who were educated in the Quran and commentary ("tafsir"), "hadith" (prophetic narrations), and the life of Muhammad. According to the "dyula" clerical tradition, a student received instruction under a single "sheikh" for a duration varying from five to thirty years, and earned his living as a part-time farmer working his teacher's lands. After he completed his studies, a "karamogo" obtained a turban and an "isnad" (teaching license), and either sought further instruction or started his own school in a remote village. A highly educated "karamogo" could become a professional "imam" or "qadi" (judge). Certain families gained a reputation for providing multiple generations of scholars. For example, the Saghanughu clan was a "dyula" lineage living in Northern and Western Ivory Coast and parts of the Upper Volta. This lineage may be traced to Timbuktu, but its principal figure was Sheikh Muhammad al-Mustafa Saghanughu (d. 1776), the "imam" of Bobo-Dyulasso. He produced an educational system based on three canonical texts of Quranic commentary ("tafsir") and "hadith". His sons continued spreading their father’s teachings and expanded through towns in Ghana and the Ivory Coast, founding Islamic schools, or madaris, and acting as "imams" and "qadis". These "madaris" were probably a positive byproduct of the long history of Muslims’ interest in literary work. In ""The Islamic Literary Tradition in Ghana"", author Thomas Hodgkin enumerates the large literary contribution that was made by Dyula-Wangara Muslims to the history of not only the regions they found themselves in but also of West Africa as a whole. He cites al-Hajj Osmanu Eshaka Boyo of Kintampo as an “"alim" with a wide range of Muslim connexions and an excellent grasp of local Islamic history” whose efforts brought together a great many Arabic manuscripts from around Ghana.