Practical Guide to the Symbolic Computation of Symmetries of   Differential Equations
  Symmetries play an critical role in finding analytic solutions to nonlinear differential equations. A symmetry is a mapping of the solutions of the differential equation into the solutions and have been studied extensively for over a century. We present a computational approach to finding symmetries and computer algebra programs to compute the usually very large system of determining partial differential equations. We also provide computer algebra algorithm that at least automatically solves most of these equations and in simple cases provides a complete solution. The algorithms are programmed in maxima/wxmaxima that is freely available. 
Stanly Steinberg, Rubens de Melo Marinho Junior
math-ph math.AP math.MP