G. Jungblut, P. A. Riezebos, and R. T. Slot boom. 1982. “An Outcrop of the Late Glacial Laacher See Ash Near Kirf (Rhineland-Palatinate)”. Netherlands Journal of Geosciences, January, 297-300. https://njgjournal.nl/index.php/njg/article/view/13504.