1. Marchuk Institute of Numerical Mathematics, Russian Academy of Sciences , Moscow , 119333 , Russia
2. Institute of Mechanics – 264 Doi Can VAST 18 Hoang Quoc Viet and University of Engineering and Technology – VNU , 144 Xuan Thuy , Hanoï , Vietnam
3. Laboratoire Jean-Kuntzmann , 51 rue des Maths, 38400 , Saint Martin d’Hères , France
4. Torus actions , 3 Avenue Didier Daurat, 31400 , Toulouse , France