Mar Rav Kadhana bar Mar Rav Chanina Gaon became head of the yeshiva in Pumbedita in year 4562 for 6 years. In that year Rav Mesharsheya bar Mar Ya'akov HaKohen ruled in Sura from year 4562 until year 4572 for nine years [(Tzemach David), and in Yuchsin in the letter of Rash"b for about 20 years and half, and he stood for three years without being a Gaon].