Currently there is not an open call of papers for this journal. This journal has published interesting articles for the period 2004 to 2009 and has got a good position at Ideas by the number of downloads per article (top 10 World position among more than 900 journals in the update of 2009-06). We are grateful to authors, referees and members of the Editorial Board for their contributions. We regret that subscriptions have not reached enough number to keep this journal going on and currently the publication is discontinued.