1. Texaco Fuels and Lubricants Technology Department, Box 1608, Port Arthur, Texas 77641
2. Wyoming Analytical Laboratories, 605 South Adams, Laramie, Wyoming 82070
3. Department of Chemical and Petroleum Engineering, The University of Calgary, Calgary, Alberta, Canada T2N 1N4
4. School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019