Peakman, T. M.; Farrimond, P.; Brassell, Simon C.; Maxwell, James R. (1986): De-A-steroids in immature marine shales. Pergamon, Oxford-New York, International, In: Leythaeuser, D. (editor), Rullkoetter, Juergen (editor), Advances in organic geochemistry 1985; Part II, Molecular and general organic geochemistry, 10 (4-6), 779-789, georefid:1987-031032