| 1 | Lie Group Analysis of Differential Equations, Volume 1, N. H. Ibragimov, Eds., CRC Press, 1993 |
| 2 | Symmetries and Differential Equations, G. W. Bluman and S. Kumei, Verlag, 1989 |
| 3 | Applications of Lie Groups to Differential Equations, Springer-Verlag, 1986 |
| 4 | Differential Equations: Their Solution Using Symmetries, H. Stephani, Cambridge University Press, 1989 |