1. Carter G. W., The Electromagnetic Field in its Engineering Aspects, 2nd edn (Longmans, London, 1967), pp. 40, 168, 169, 172, 340.
2. Duffin W. J., Electricity and Magnetism, 4th edn (McGraw-Hill, New York, 1990), p. 209.
3. Cullwick E. G., The Fundamentals of Electromagnetism (Cambridge University Press, Cambridge, 1949), pp. 100, 115–116, 129.
4. Hammond P., Electromagnetism for Engineers, 3rd edn (Pergamon Press, Oxford, 1993), p. 160.