Department of Theoretical Physics and IFIC – University of Valencia and CSIC, Spain

Dpto. Matemáticas, Facultad de Matemáticas, University of Valencia, Spain

Institut d’Astronomie et d’Astrophysique, CP-226, Université Libre de Bruxelles, Belgium

Louisiana State University, Baton Rouge, United States

U. Valladolid

Universidad Complutense de Madrid, Madrid, Spain

Department of Astronomy and Astrophysics, Faculty of Physics, University of Valencia, Spain

Inter-University Center for Astronomy and Astrophysics, India

University of Wroclaw, Poland

Sternberg Astronomical Institute, Lomonosov Moscow State University

INFN Sezione di Catania, Italy