NASA - Goddard Space Flight Center (GSFC), February 11, 2003
Institute for Advanced Study (IAS), Princeton, February 13, 2003
1st ENIGMA meeting, Mayschoss, Germany, May 11-14, 2003
Hel.A.S. meeting, Penteli, Greece, September 15-17, 2003
Virtual Astrophysical Jets meeting, Dogliani, Italy, October 2-4, 2003
4th ENIGMA meeting, Perugia, Italy, October 6-8, 2004
Gamma-Ray Burst in the Afterglow Era, 4th Workshop, Rome, Italy, October 18-22, 2004
Blazar Variability Workshop II: Entering the GLAST Era, Miami, April 10-12, 2005
National Observatory of Athens, May 19, 2005
Hel.A.S. meeting, Kefallinia, Greece, September 8-11, 2005
6th ENIGMA meeting, Kinsale, Ireland, November 22-25, 2005
SWIFT and GRBs: Unveiling the Relativistic Universe, Venice, Italy, June 5-9, 2006
Challenges of relativistic jets, Cracow, Poland, June 25-July 1, 2006
First X-ray Astronomy School, National Observatory of Athens, September 18-20, 2006
4th JETSET Summer School: From models to observations and experiments, Azores, Portugal, June 25-29, 2007
Hel.A.S. meeting, Thassos, Greece, September 13-15, 2007
High Energy Phenomena in Relativistic Outflows, Dublin, Ireland, September 24-28, 2007
RCAAM, Academy of Athens, Greece, February 21, 2008
University of Heidelberg, Heidelberg, Germany, May 27, 2008
The Central Kiloparsec: Active Galactic Nuclei and Their Hosts, Ierapetra, Greece, June 4-6, 2008
Protostellar Jets in Context, Rhodes, Greece, July 7-12, 2008
Astronomy School "The many faces of AGN", National Observatory of Athens, September 22-24, 2008
Frontiers of Space Astrophysics: Neutron Stars & Gamma Ray Bursts, Cairo & Alexandria, Egypt, March 30 - April 4 2009
Hel.A.S. meeting, Athens, Greece, September 20-24, 2009
Dipartimento di Fisica Generale, Turin, Italy, January 27, 2010
Frontiers of Nonlinear Physics, Russia, July 14, 2010
RCAAM, Academy of Athens, Greece, April 12, 2011
Edo and friends, Turin, Italy, April 29, 2011