1. Very High Energy Cosmic Rays and Their Interactions
2. Eg.L. Jones, proceedings of ISVHECRI94, Tokyo (1994)
3. The NEEDS workshop, Karlsruhe 2002, http://www-ik.fzk.de/~needs/
4. The C2CR workshops, in 2005 in Prague http://www.particle.cz/conferences/c2cr2005/ and 2007 in Granlibakken http://www.physics.ucdavis.edu/~c2cr07/C2CR07/home.html
5. A. De Roeck, talk at this conference