Patricia Crone states, "there is no doubt that Mohammed existed, occasional attempts to deny it notwithstanding," and notes Byzantine sources that mentioned an Arab prophet. Michael Cook takes the view that evidence independent of Islamic tradition "precludes any doubts as to whether Muhammad was a real person" and clearly shows that he became the central figure of a new religion in the decades following his death. He reports, though, that this evidence conflicts with the Islamic view in some aspects, associating Muhammad with Israel rather than Inner Arabia, complicating the question of his sole authorship or transmission of the Quran, and suggesting that there were Jews as well as Arabs among his followers. For Crone, a single Greek text written at around the time of Muhammad's death provides "irrefutable proof" that he was a historical figure. There is also, she says, "exceptionally good" evidence that Muhammad was an Arab political leader and prophet. She says we can be "reasonably sure" in attributing all or most of the Quran to him. She takes a view that Muhammad's traditional association with the Arabian Peninsula may be "doctrinally inspired", and is put in doubt by the Quran itself, which describes agricultural activity that could not have taken place there, as well as making a reference to the site of Sodom which appears to place Muhammad's community close to the Dead Sea.