W. H. Zagwijn, H. M. Montfrans, and J. G. van Zandstra. “Subdivision of the "Cromerian" in the Netherlands; Pollen-Analysis, Palaeomagnetism and Sedimentary Petrology ”. Netherlands Journal of Geosciences (January 1, 1971): 41-58. Accessed August 28, 2026. https://njgjournal.nl/index.php/njg/article/view/14793.