John W.M. Jagt, and Ger P.H. Michels. “Cyclaster Platornatus Kutscher, 1978: An Addition to the Echinoid Fauna from the Late Maastrichtian of NE Belgium”. Netherlands Journal of Geosciences, Jan. 1987, pp. 57-63, https://njgjournal.nl/index.php/njg/article/view/13092.