1. Padovani, C., Berti, V. and Prinetti, A. 1959. V World Petrol. Cong. 1959, New York. pp.p. 275 Proceedings Sec. V, Paper 21
2. Takeuchi, C. 1982. UNITAR, Int. Conf. Heavy Crude and Tar Sands, Upgrading Session. February1982, Caracas.
3. Pruden, B. B. 1990. Oilsands 2000 Conference. March1990.
4. Guitian, J. 1990. AIChe Meeting. August1990, San Diego.