 For example, the most important historiographical source for the origins of Islam is the work of al-Tabari.While al-Tabari is considered an excellent historian by the standards of his time and place, he made liberal use of mythical, legendary, stereotyped, distorted, and polemical presentations of subject matter—which are however considered to be Islamically acceptable—and his descriptions of the beginning of Islam post-date the events by several generations, al-Tabari having died in 923.Differing views about how to deal with the available sources has led to the development of four different approaches to the history of early Islam.