1. Lundbeck Foundation Center for Theoretical Chemistry, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Århus C, Denmark
2. Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, I-34127 Trieste,
Italy
3. Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, 80309-0215