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Bernoulli, Daniel; Schaltegger, Urs; Stern, Willem B.; Frey, Martin; Caron, Michèle; Monechi, Simonetta (2004). Volcanic ash layers in the Upper Cretaceous of the Central Apennines and a numerical age for the early Campanian. International journal of earth sciences, 93(3), pp. 384-399. Springer-Verlag 10.1007/s00531-004-0389-4
