A model equation for ultrashort optical pulses around the zero dispersion frequency S. Amiranashvili, A. G. Vladimirov and U. Bandelow Eur. Phys. J. D, 58 2 (2010) 219-226 Published online: 26 January 2010 DOI: 10.1140/epjd/e2010-00010-3