1. Maxwell, J.C.: Electricity and Magnetism, (MacMillan 1873),2, p. 291
2. Russell, A.: A Treatise on the Theory of Alternating Currents, 2nd edn(Cambridge University Press 1914),1, Ch. 7,
3. McLachlan, N.W.: Bessel Functions for Engineers, (Clarendon 1934),Ch. 9,
4. Carter, G.W.: The Electromagnetic Field in its Engineering Aspects, (Longmans 1958), p. 215