 Complete the following phrase:  Sezgin earned his PhD from Istanbul University under the German Orientalist Hellmut Ritter in 1950. His thesis titled Buharinin Kaynakları The Sources of Al-Bukhari argued that, contrary to the common belief among European orientalists, Al-Bukharis edition of collected Hadiths was based on written sources dating back to the 7th century as well as oral history. He obtained a position at Istanbul University, but was dismissed in the wake of the 