Laboratoire de Physique Mathématique, Université de Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France; polarski(at)LPM.univ-montp2.fr
Received 23 September 2003, revised 24 October 2003, accepted 26 October
2003 by F. W. Hehl
(1) Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden, Germany; pz(at)mpipks-dresden.mpg.de; (2) Leibniz-Institut für Festkörper- und Werkstofffroschung, Dresden, Germany, and University of Debrecen, Hungary
Received 1 August 2003, accepted 8 November 2003 by B. Kramer
Institut für Theoretische Physik, Freie Universität Berlin, 14195 Berlin, Germany; ieremin(at)physik.fu-berlin.de; etc.
Received 1 September 2003, revised 10 December 2003, accepted
23 December 2003 by U. Eckern
(approx. 28 pages)