The Spanish Ministry of Science and Technology supported this
work through the projects AGL2006-04775 and AGL2010-21572.
The Human Resources Coordination of the University of Oriente,
Venezuela, provided a grant for doctoral studies to Ana Yndira
Ramos Villarroel, and the University of Lleida provided a Jade Plus
grant. The ICREA Academia Award to Professor Olga Martín-Belloso
is also acknowledged.