Hoffmann , N., H. Jödicke, and P. Gerling. “The Distribution of Pre-Westphalian Source Rocks in the North German Basin – Evidence from Magnetotelluric and Geochemical Data”. Netherlands Journal of Geosciences, vol. 80, no. 1, Apr. 2001, pp. 71-84, doi:10.1017/S0016774600022174.