On parametrization and mixture laws for electron ionization coefficients D. Marić, M. Radmilović-Radenović and Z. Lj. Petrović Eur. Phys. J. D, 35 2 (2005) 313-321 Published online: 28 June 2005 DOI: 10.1140/epjd/e2005-00172-y