1. Consultant, Caracas, Venezuela. Present address: AICISE, Chemical and Petroleum Engineering Department, Calgary University, 2500 University Drive N. W., Calgary, Alberta, T2N 1N4, Canada
2. Branch of Molecular Engineering Research, Mexican Institute of Petroleum, Eje Central Lazaro Cardenas152, Col. San Bartolo Atepehuacan C. P. 07730, Mexico D. F., Mexico