1. W. Hittorf, Ann. Phys. Chem. 21, 90 (1884)
2. H.W. Loeb, J. Spacecraft Rockets 8, 494 (1970)
3. R. Killinger, H. Leiter, R. Kukies, in the 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Cincinnati, OH, 2007
4. M. Kilter, A. Karlsson, in Proceedings of the 4th International Spacecraft Propulsion Conference, Sardinia, Italy, 2004
5. H. Leiter et al., in the 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, CA, 2011