Carter, Robert A. and Philip, Graham Beyond the Ubaid: Transformation and Integration in the Late Prehistoric Societies of the Middle East (Studies in Ancient Oriental Civilization, Number 63) The Oriental Institute of the University of Chicago (2010) ISBN 978-1-885923-66-0 p.2, at http://oi.uchicago.edu/research/pubs/catalog/saoc/saoc63.html （页面存档备份，存于互联网档案馆）; "Radiometric data suggest that the whole Southern Mesopotamian Ubaid period, including Ubaid 0 and 5, is of immense duration, spanning nearly three millenia from about 6500 to 3800 B.C."
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Carter, Robert A. and Philip, Graham Beyond the Ubaid: Transformation and Integration in the Late Prehistoric Societies of the Middle East (Studies in Ancient Oriental Civilization, Number 63) The Oriental Institute of the University of Chicago (2010) ISBN 978-1-885923-66-0 p.2, at http://oi.uchicago.edu/research/pubs/catalog/saoc/saoc63.html （页面存档备份，存于互联网档案馆）; "Radiometric data suggest that the whole Southern Mesopotamian Ubaid period, including Ubaid 0 and 5, is of immense duration, spanning nearly three millenia from about 6500 to 3800 B.C."
