1. Adams, W. N., and Pitts, G. J., Fuel, 34, 383 (1955).
2. Blom, L., Edelhausen, L., and van Krevelen, D. W., Fuel, 36, 135 (1957).
3. van Vucht, H. A., Rietveld, B. J., and van Krevelen, D. W., Fuel, 34, 50 (1955).
4. Bergman, G., Huck, G., Karweil, J., and Luther, H., Brennstoff- Chemie, 38, 193 (1957).
5. Unpublished work. See also Monnot, G. A., and Morel, P., Applied Spectroscopy, 9, 180 (1955).