A Lithostratigraphic subdivision of the Lower Triassic in the Northwest German lowlans and the German sector of the North Sea, based on gamma-ray and sonic logs : / Heinz-Gerd Röhling. The Perennial Rotliegend Saline Lake in Northwest Germany. / Reinhard E. Gast. - Röhling, Hein-Gerd (Schweizerbart, 1991)