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2. Symmetries and Differential Equations;Bluman,1989
3. Application of Lie Groups to Differential Equations;Olver,1989
4. N.H. Ibragimov, Elementary Lie Group Analysis and Ordinary Differential Equations, John Wiley and Sons Ltd, Chichester, 1999.
5. N.H. Ibragimov (Ed.), CRC Handbook of Lie Group Analysis of Differential Equations, vols. 1–3, CRC Press, Boca Raton, 1994, 1995, 1996.