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