1. Applications of Lie Groups to Differential Equations;Olver,1993
2. Group Analysis of Differential Equations;Ovsyannikov,1982
3. Symmetry and Integration Methods for Differential Equations;Bluman,2004
4. The general similarity solution of the heat equation;Bluman;J. Math. Mech.,1969
5. New classes of symmetries for partial differential equations;Bluman;J. Math. Phys.,1988