Philip L. Gibbard, Martin J. Head, Michael J. C. Walker: Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma. Journal of Quaternary Science, 2010, nro 2, s. 96–102. doi:1 0.1002/jqs.1338ISSN 1099-1417Artikkelin verkkoversio. (englanniksi)
Philip L. Gibbard, Martin J. Head, Michael J. C. Walker: Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma. Journal of Quaternary Science, 2010, nro 2, s. 96–102. doi:1 0.1002/jqs.1338ISSN 1099-1417Artikkelin verkkoversio. (englanniksi)
worldcat.org
Philip L. Gibbard, Martin J. Head, Michael J. C. Walker: Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma. Journal of Quaternary Science, 2010, nro 2, s. 96–102. doi:1 0.1002/jqs.1338ISSN 1099-1417Artikkelin verkkoversio. (englanniksi)