The main way to work out the chronology is to use the ancient Egyptian lists of kings. The number of years each king ruled, regnal years, can be added up. However there are problems with these lists. Some, such as the "Turin King List", are quite detailed but they are not complete. The whole of "Abydos King List" has survived, but it does not have a complete list of rulers. Sometimes different versions of the same text are different. For example, Manetho's history of Egypt has not survived. Later writers such as Eusebius and Sextus Julius Africanus used Manetho's work for their histories, but their dates for the same ruler are often very different.