“…Among of them, (21), (23), and (24) are equivalent to (27), (28), and (29), respectively. However, as demonstrated above, (20) and (22) with an explicit linear function in ξ are different from (27) - (29) and cannot be obtained by the (G /G)-expansion method [25, 26, 28 -31] and its improvements [27,36] if we don't transform (13) into (14) but directly solving (13).…”