Pineda, M. C.
Viloria, J.
MartÃnez-Casasnovas, J. A.
Funding for this research was provided by:
Abdus Salam International Centre for Theoretical Physics
Council of Scientific and Humanistic Development (CDCH) of the Universidad Central de Venezuela
Venezuelan Organic Law for Science and Technology LOCTI
Universidad de Lleida (Catalonia, Spain)