1. J.B. Hasted: Physics of Atomic Collisions (Butterworths, London 1964)
2. E.D. Lozansky, O.B. Firsov: Theory of Sparks (Atomizdat, Moscow 1975)
3. A. von Engel: Handbuch der Physik Bd. 21 (Springer, Berlin 1956)
4. AL. Ward: J. Appl. Phys. 33, 2789 (1962)
5. A. von Engel: Ionized Gases (Clarendon, Oxford 1965)