J.J.P. Zijlstra, M.H.M.P. Brouwers, H. Brinkhuis, and P.L. de Boer. “Microfacies Analysis of Cretaceous/Tertiary Boundary Sections in the Quarries Geulhemmerberg and Curfs, SE Netherlands”. Netherlands Journal of Geosciences, vol. 75, Jan. 1996, pp. 133-51, https://njgjournal.nl/index.php/njg/article/view/12367.