1. Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)
2. Present address: School of Chemistry & Physics, The University of Adelaide, North Terrace, Adelaide, SA 5005 (Australia), Fax: (+61) 8‐8303‐4358
3. Agriculture and Life Sciences Division, Lincoln University, Post Office Box 84, Canterbury (New Zealand), Fax: (+64) 3‐325‐3851
4. Present address: Institute of Polymer Research, GKSS Research, Centre Geesthacht GmbH, Kantstrasse 55, 14513 Teltow (Germany)