Comment on: “Some exact solutions of KdV equation with variable coefficients” [Commun Nonlinear Sci Numer Simul 2011;16:1783–86]

It is shown that in the commented paper the exact solutions were found only for those variable-coefficient KdV equations which are reduced to the classical (constant-coefficient) KdV equation by point transformations, and these solutions are preimages of well-known traveling wave solutions of the KdV equation with respect to the corresponding point transformations. The equivalence-based approach suggested in [Popovych RO, Vaneeva OO. More common errors in finding exact solutions of nonlinear differential equations: Part I. Commun Nonlinear Sci Numer Simul 2010;15:3887–99] allows one to obtain more results. This disproves the relevance of the extended mapping transformation method for the class of equations under consideration.