1. Mathematical Institute, Charles University, Sokolovská 83, CZ-186 75 Praha 8, Czech Republic and Institute of Thermomechanics, Czech Academy of Sciences, Dolejškova 5, CZ-18200 Praha 8, Czech Republic.
2. Faculty of Mathematics, University of Vienna, Oskar-Morgenstern-Platz 1, 1090 Vienna, Austria, Vienna Research Platform on Accelerating Photoreaction Discovery, University of Vienna, Währingerstrasse 17, A-1090 Vienna, Austria, and Istituto di Matematica Applicata e Tecnologie Informatiche E. Magenes - CNR, v. Ferrata 1, 27100 Pavia, Italy.