1. Heun’s Differential Equations, A. Ronveaux, Ed., London: Oxford University Press, 1995.
2. NIST Handbook of Mathematical Functions, F.W.J. Olver, D.W. Lozier, R.F. Boisvert, C.W. Clark, Eds., New York: Cambridge University Press, 2010.
3. Léauté, B. and Marcilhacy, G., J. Phys. A, 1986, vol. 19, p. 3527.
4. Pons, R. and Marcilhacy, G., Class. Quantum Grav., 1987, vol. 4, p. 171.
5. Ishkhanyan, A.M. and Suominen, K.-A., J. Phys. A, 2001, vol. 34, p. 6301.