invitation to be the Guest Editors for these Special Issues of ECOS 2009. We also would like to thank the Associate Editors-in-Chief Prof. Derek K. Baker and Prof. Murat Köksal who put in a huge effort in the preparation of these issues. Finally, we are deeply grateful to all the people that contributed to this event: the participants, session chairs, lecturers and particularly the reviewers, who continued working for these Special Issues. We took into account their opinions to recommend 20 papers for submission to the journal from the 230 papers included in the Proceedings