1. Department of Chemistry, University of Oulu, P. O. Box 3000, 90014 Oulu, Finland, Fax: +358‐8‐553‐1608
2. Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada
3. Department of Chemistry, University of Jyväskylä, P. O. Box 35, 40014 Jyväskylä, Finland
4. Department of Chemistry, University of Joensuu, P. O. Box 111, 80101 Joensuu, Finland