Seven common errors in finding exact solutions of nonlinear differential equations
where x0 is arbitrary constant.
Example 6b. Solution of the foam drainage equation by Bekir and Cevikel 
Using the travelling wave
they obtained the first - order equation in the form
and obtained three solutions
The solution of Eq.(7.7) can be found using the transformation . For function we obtain the Riccati equation in the form
Solution of Eq.(7.9) can be written as
We can see there are the misprints in solutions of Eq.(7.7)
Example 6c. ”Solutions” of the Fisher equation by Öziş and Köroǧlu 
However all these expressions do not satisfy equation (7.11). We can note this fact without substituting solutions (7.12) - (7.15) into Eq. (7.11), because a true solution of Eq. (7.11) has the pole of the second order, but all functions (7.12) - (7.15) are the first order poles and certainly by substituting expressions (7.12) - (7.15) into equation (7.11) we do not obtain zero.
The general solution of Eq.(6.4) can be found via the Jacobi elliptic function, but the author tried to obtain some solitary solutions by means of the Exp - function method using the travelling wave , . Some of his solutions are incorrect. For example the ”solution” (formula (3.12) )
do not satisfy Eq.(6.4).
The solution of Eq.(6.4) takes the form
This solution can be obtained by using different methods.
Example 6e. ”Solutions” of the Burgers - Huxley equation by Chun .
Chun  applied the Exp - function method to obtain the generalized solitary wave solutions of the Burgers — Huxley equation
In the travelling wave the author looked for the solution of equation
where . Some of the solutions by Chun are incorrect. In particular, ”solution” (25) in 
Example 6f. ”Solutions” of the Benjamin - Bona - Mahony - Burgers equation by El-Wakil, Abdou and Hendi .
El-Wakil and co-authors  using the Exp - function method looked for the solitary wave solutions of the BBMB equation
Taking the travelling wave the authors searched for the solution of the equation
Some of solutions by El-Wakil and co-authors are incorrect. In particular, expression (18) in 
do not satisfy Eq.(7.22).
where C2 is an arbitrary constant. Eq.(7.24) coincides with the KdV - Burgers equation in the travelling wave. The solitary wave solutions of this equation are given above in section 1. The general solution of Eq.(7.24) can be found by analogue with the general solution of Eq.(2.7) .
Example 6g. ”Solutions” of the Klein — Gordon equation with quadratic nonlinearity by Zhang .
The Exp - function method was used by Zhang to obtain the generalized solitonary solutions of the Klein - Gordon equation with the quadratic nonlinearity
The author  applied the travelling wave and searched for the solution of the equation
where is an arbitrary constant.
Example 6h. ”Solutions” of the Kuramoto - Sivashinsky equation by Noor, Mohyud - Din and Waheed .
Using the Exp - function method Noor, Mohyud-Din and Waheed  looked for the solutions of the Kuramoto—Sivashinsky equation
These authors presented two expressions as the solutions of the Kuramoto - Sivashinsky equation. Their first ”solution” is written as
where a0, , k are arbitrary constants (formula (26) in ).
The second ”solution” by the authors takes the form
where a0, a-2, a2, b0, b2, , k are arbitrary constants (formula (34) in ).
Here we have the sixth common error in the fatal form. Substituting cited ”solutions” (7.32) and (7.33) into (7.31), we obtain that these ”solutions” do not satisfy the Kuramoto - Sivashinsky equation. Moreover, we cannot obtain zero with any nontrivial values of the parameters. We guess, that using the Exp - function method the authors  did not solve the system of the algebraic equations for the parameters.
where C0 and x0 are arbitrary constants.
Many authors tried to find new exact solutions of the Kuramoto - Sivashinsky equation (7.31). Some of authors [36, 74, 75] believe that they found new solutions but it is not this case. Nobody cannot find new exact solutions of Eq.(7.31).
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