Extended Jacobi elliptic function method and its applications to (2+1)﹣dimensional dispersive long-wave equation

An extended Jacobi elliptic function method is proposed for constructing the exact double periodic solutions of nonlinear partial differential equations (PDEs) in a unified way. It is shown that these solutions exactly degenerate to the many types of soliton solutions in a limited condition. The Wu－Zhang equation (which describes the (2+1)﹣dimensional dispersive long wave) is investigated by this means and more formal double periodic solutions are obtained.