Papyrus is by now so disputed that we must ask ourselves whether we really possess a sure basis for the chronology of this period of Egyptian history which is, after all, of the greatest importance for fixing the sequence of historical events, as well as for neighbouring countries". Professor Wolfgang Helck concludes that "We therefore think it is safer to start from the regnal dates rather than from interpretations of real or supposed Sirius (Sothic) or New Moon dates". Papyrus Leiden I.350, which dates to the 52nd year of Ramesses II, records a lunar observation which places that year of Ramesses's reign in one of 1278, 1253, 1228 or 1203 BC within the date-range of the conventional chronology. Having questioned the value of the Ebers Papyrus, Rohl argues that, since the lunar cycle repeats itself every 25 years, it is only useful for fine tuning a chronology and could equally apply to dates 300 years later as in the New Chronology. Thus, Rohl is of the opinion that none of these three foundations of the conventional Egyptian chronology are secure, and that the sacking of Thebes by the Assyrian king Ashurbanipal in 664 BC is the earliest fixed date in Egyptian history. Evidence adduced Rohl bases his revised chronology (the New Chronology) on his interpretation of numerous archeological finds and genealogical records from Egypt. For example: Rohl notes that no Apis bull burials are recorded in the Lesser Vaults of the Serapeum of Saqqara for the Twenty-first and early Twenty-second Dynasties. He also argues that the reburial sequence of the mummies of the New Kingdom pharaohs in the Royal Cache (TT 320) shows that these two dynasties were contemporary (thus explaining why there are too few Apis burials for the period). Rohl finds that in the royal burial ground at Tanis it appears that the tomb of Osorkon II of the 22nd Dynasty was built before that of Psusennes I of the 21st Dynasty; in Rohl's view this can only be explained if the two dynasties were contemporary. Rohl offers inscriptions that list three non-royal genealogies which, when one attributes 20 to 23 years to a generation, show, according to Rohl, that Ramesses II flourished in the 10th century BC as Rohl advocates. In the conventional chronology, all three genealogies would be missing seven generations. He also argues that there are no genealogies that confirm the conventional dates for Ramesses