1. Potthof, K.W.: ‘Inception of corona at low surface gradients’, Forrest, J.S., Howard, P.R., Littler, D.J., Gas discharges and the electricity supply industry, (Butterworths 1962), p. 219–224
2. Peek, F.W.: Dielectric phenomena in h.v. engineering, 3rd edn(McGraw-Hill 1929)