Nijenhuis, I. A.; Bosch, H. J.; Sinninghe Damste, J. S.; Brumsack, H. J.; de Lange, G. J. (1999): Organic matter and trace element rich sapropels and black shales; a geochemical comparison. Elsevier, Amsterdam, Netherlands, Earth and Planetary Science Letters, 169 (3-4), 277-290, georefid:1999-043446