A note on New kink-shaped solutions and periodic wave solutions for the (2+1)-dimensional Sine-Gordon equation

Exact solutions of the Nizhnik-Novikov-Veselov equation by Li [New kink-shaped solutions and periodic wave solutions for the (2+1)-dimensional Sine-Gordon equation, Appl. Math. Comput. 215 (2009). 3777-3781] are analyzed. We have observed that fourteen solutions by Li from thirty do not satisfy the equation. The other sixteen exact solutions by Li can be found from the general solutions of the well – known solution of the equation for the Weierstrass elliptic function. In the paper [1], Li looked for the exact solutions of the nonlinear evolution equatio