Reduction operators and exact solutions of variable coefficient   nonlinear wave equations with power nonlinearities
  Reduction operators, i.e. the operators of nonclassical (or conditional) symmetry of a class of variable coefficient nonlinear wave equations with power nonlinearities is investigated within the framework of singular reduction operator. A classification of regular reduction operators is performedwith respect to generalized extended equivalence groups. Exact solutions of some nonlinear wave model which are invariant under certain reduction operators are also constructed. 
Ding-jiang Huang, Qin-min Yang and Shui-geng Zhou
math-ph math.MP