1. L. B. Davin, H.-B. Wang, A. L. Crowell, D. L. Bedgar, D. M. Martin, N. G. Lewis, Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
2. S. Sarkanen, University of Minnesota, Department of Wood and Paper Science, Kaufert Laboratory, St. Paul, MN 55108, USA.