Völk, Heinrich J. Prof. Heinrich J. Völk, Emeriti, MPI for Nuclear Physics, Max Planck Society;
http://pos.sissa.it/archive/conferences/123/139/Texas%202010_139.pdf (Any fulltext)
Völk, H. J., & Lisenfeld, U. (2011). Shock acceleration of relativistic particles in galaxy-galaxy collisions. Proceedings of Science, Texas2010: 139, 1-7.