1. W. K. H. Panofsky and M. Phillips,Classical Electricity and Magnetism(Addison-Wesley, Cambridge, Mass., 1955), p. 138.
2. H. Lamb,Hydrodynamics(Dover, New York, 1945), p. 473.
3. L. M. Milne-Thomson,Theoretical Hydrodynamics(Macmillan, New York, 1968), 5th ed., p. 287.