“…Obtaining their explicit solutions is quite di cult. So far, with the development of soliton theory, many e cient methods for obtaining these exact solutions have been presented, such as Hirota bilinear tranformation [1], Darboux and Backlund transform [2], Weierstrass function method [3], symmetry method [4,5], Painleve analysis method [6], theta function method [7], Wronskian technique [8], homogeneous balance method [9,10], F-expansion method [11], sine-cosine method [12,13], exponential function method [14,15], inverse scattering method [16,17], functional variable method [18], extended tanh method [19], modi ed simple equation method [20,21], trial equation method [22], (G ′ /G)-expansion method [23,24], sub-equation method [25], auxiliary equation method [26] and so on. When we nd the exact solutions of nonlinear partial di erential equations by using the (G ′ /G)-expansion method, we obtain the solution in the terms of (G ′ /G).…”