1. Down, A. L., and G.W. Himus: Classification of oil shales and cannel coals. J. Inst. Petrol. 26, 329–348 (1940).
2. Quass, F. W.: The analysis of the kerogen of oil shales. J. Inst. Petrol. 25, 813–819 (1939).
3. Himus, G. W., and G.C. Basak: Analysis of coals and carbonaceous materials containing high percentages of inherent mineral matter. Fuel 28,57–64 (1949).
4. Smith, J. W, and L. W. Higby: Preparation of organic concentrate from Green River oil shale. Anal. Chem. 32, 17–18 (1960).
5. Robinson, W. E, and G. U. Dinneen: Constitutional aspects of oil-shale kerogen. Proc. 7th World Petroleum Congress, Mexico City, Mexico No. 3, 669–680 (April 1967).