Westerhold, T, Röhl, U, Raffi, I, Fornaciari, E, Monechi, S, Reale, V, Bowles, J and Evans, HF (2008) Astronomical calibration of the Paleocene time. Palaeogeography, Palaeoclimatology, Palaeoecology, 257(4). 377-403. doi:10.1016/j.palaeo.2007.09.016