Pross et al., 2010
From dinoflaj3
Pross, J., Houben, A.J.P., van Simaeys, S., Williams, G.L., Kotthoff, U. and Coccioni, R., 2010: Umbria-Marche revisited: a refined magnetostratigraphic calibration of dinoflagellate cyst events for the Oligocene of the western Tethys. Review of Palaeobotany and Palynology, v.58, p.213-235, pl.1-4.