E. B. A. Bisdom, A. Gerlofsma, J. N. B. Poelman, and P. A. Riezebos. “Composite Grains in Heavy-Mineral Concentrates and Their Significance in the Differentiation of Surface Deposits at the Confluence of the Maas (Meuse) and Roer (Rur) Rivers.”. Netherlands Journal of Geosciences (January 1, 1978): 407-416. Accessed March 31, 2026. https://njgjournal.nl/index.php/njg/article/view/14167.