1. G.N. Watson, A Treatise on the Theory of Bessel Functions (Cambridge University Press, 1946) p. 6.
2. H. Jeffrey & B.S. Jeffrey, Methods of Mathematical Physics (Cambridge University Press, 1946) p. 492.
3. Laplace, Mécanique Céleste, livre 11, supplément 1. [Reference given by G.N. Watson, Camb. Phil. Trans. 22 (1918) 290].
4. M.C. Gray and S.A. Schelkunoff, Bell Syst. Tech. J. 27 (1948) 350.
5. Lord Rayleigh, The Theory of Sound, Vol. II, (Macmillan, London, 1896) p. 68.