1. Tipman, R. N.; Shaw, R. C.Our Petroleum Future Conference, Edmonton, April 4–7 1993.
2. Taciuk, W.; Caple, R.; Goodwin, S.; Taciuk, G.U.S. Patent 5,366,596, 1994.
3. Graham, R. J.; Helstrom, J. J.; Mehlberg, R. L.Eastern OH Shale Symposium, Hyatt Regency, Lexington, Kentucky, Nov 18–20 1987; pp93–99.
4. Rosenbloom, W. J.U.S. Patent 5,534,136, 1996.