W. H. Zagwijn, H. M. Montfrans, & J. G. van Zandstra. (1971). Subdivision of the "Cromerian" in the Netherlands; pollen-analysis, palaeomagnetism and sedimentary petrology . Netherlands Journal of Geosciences, 41-58. Retrieved from https://njgjournal.nl/index.php/njg/article/view/14793