M. Beck, and F. Dausinger. European Scientific Laser Workshop on Mathematical Simulation, page 201 - 216. Coburg, Sprechsaal Publishing Group, (September 1989)
P. Berger, H. Hügel, and T. Graf. Lasers in Manufacturing 2011, 12, Part A, page 0. Amsterdam, Wissenschaftliche Gesellschaft Lasertechnik e.V., Elsevier Ltd., (2011)