Spectroscopic investigations of back-corona discharge on fly-ash layer T. Czech, M. Lackowski, A. Krupa, A. T. Sobczyk, A. Jaworek and E. Rajch Eur. Phys. J. D, 54 2 (2009) 425-432 Published online: 06 February 2009 DOI: 10.1140/epjd/e2009-00014-0