Afrouzi , G. A.Heidarkhani , S.Hadjian , A. and Shakeri , S.. (2012). On a Class of Neumann Boundary Value Equations Driven by a (p<sub>1</sub>, , P<sub>n</sub>)-Laplacian Operator.
            <i>Journal of Partial Differential Equations</i>. <i>25</i> (1).
            21-31.
         doi:10.4208/jpde.v25.n1.2