H.B. Vonhof, J.W.M. Jagt, A. Immenhauser, J. Smit, Y.W. van den Berg, M. Saher, N. Keutgen and J.J.G. Reijmer 2011. Belemnite-based strontium, carbon and oxygen isotope stratigraphy of the type area of the Maastrichtian Stage. Netherlands Journal of Geosciences. 90, (Nov. 2011), 259 - 270. DOI:https://doi.org/10.1017/S0016774600001141.