1. Levi-Civita, T.: Acta Math. 42, 99–144 (1920)
2. Daboul, J., Nieto, M.M.: Phys. Rev. E52, 4430–4440 (1995). hep-th/9408057
3. Nieto, M.M., Daboul, J.: Exact, E=0, classical and quantum solutions for general power-law oscillators. In: Proceedings of the Second International Workshop on Harmonic Oscillators, Cocoyoc, 23-25 March 1994
4. In: Han, D., Wolf, K.B. (eds.) Nasa Conference Publications, vol. 3286, pp. 13-24 (1995). hep-th/9406088
5. Xin, J.-L., Liang, J.-Q.: Chin. Phys. B21, 040303 (2012). doi:10.1088/1674-1056/21/4/040303; hep-th/1010.4352 contains more clear colored pictures than in the journal