1. H. Jeffreys, Monthly Notices of the Royal Astronomical Society. Geophysical Supplement. vol. 2 (1928) pp. 101-111.
2. \bysameBritish Association Tables, Part Volume B, J. C. P. Miller, 1946.
3. On the asymptotic solutions of differential equations, with an application to the Bessel functions of large complex order;Langer, Rudolph E.;Trans. Amer. Math. Soc.,1932
4. Uniform asymptotic expansions;Cherry, T. M.;J. London Math. Soc.,1949
5. F. Tricomi, Sulle funzioni di Bessel di ordine e argomento pressoche uquali, Atti della Accademia delle Scienze di Torino vol. 83 (1947-1948).