1. University of Houston, 617 Science and Research Building 1, Houston, Texas 77204.
2. Montclair State University, Department of Mathematical Sciences, 1 Normal Avenue, Montclair, New Jersey 07043.
3. Statoil Research Center, N-7005 Trondheim, Norway.
4. Indiana University, Bloomington, 1001 East 10th Street, Bloomington, Indiana 47405.