1. Department of Chemistry, Texas A&M University, P. O. Box 30012, College Station, Texas 77842‐3012, USA, Fax: (internat.) + 1‐979/845‐7177
2. Instituto de Ciencia Molecular, Universidad de Valencia, Dr. Moliner, 50, Burjassot 46100, Spain, Fax: (internat.) + 34‐96/386‐4859