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[2] Bonanno G, Riccobono G. Multiple results for Sturm-Liouville boundary value problems.Appl Math Comput, 2009, 210: 294--297

[3] Bonanno G, Marano S A. On the structure of the critical set of non-differential functionals with a weak compactness condition.  Appl Anal, 2010, 89: 1--10

[4] Tian Y, Ge W. Second-order Sturm-Liouville boundary value problem involving the one-dimensional $p$-Laplacian.Rocky Mountain J Math, 2008, 38: 309--327

[5] Bonanno G, Chinn\`{i} A. Existence of three solutions for a perturbed two-point boundary value problem,Applied Mathematics Letter, 2010, 23: 807--811

[6] Bonanno G, D'Agu\`{i} G. Multiplicity results for a perturbed elliptic Neumann problem.  Abstract and Applied Analysis, 2010, 2010: 1--10

[7] D'Agu\`{i} G. Existence results for a mixed boundary value problem with  Sturm-Liouville equation.  Adv Pure Appl Math, 2011: 237--248

[8] D'Agu\`{i} G. Multiplicity results for nonlinear mixed boundary value problem.  Bound Value Probl, 2012, 12: 2012--134

[9] D'Agu\`{i} G. Infinitely many solutions for a double Sturm-Liouville problem. J Global Optimization, 2012, 54: 619--625

[10] Bonanno G, Chinn\`{i} A. Existence of three solutions for a perturbed two-point boundary value problem. Appl Math Lett,2010, 23: 807--811

[11] Bonanno G, Motreanu G, Winkert P. Variational-hemivariational inequalities with small  perturbations ofnonhomogeneous Neumann boundary conditions.  J Math Anal Appl, 2011, 381: 627--637

[12] D'Agu\`{i} G, Sciammetta A. Infinitely many solutions to elliptic problems with variable exponent and nonhomogeneous Neumann conditions. Nonlinear Anal, 2012, 75: 5612--5619

[13] Heidarkhani S, Tian Y. Multiplicity results for a class of gradient systems depending on two parameters.  Nonlinear Anal, 2010, 73: 547--554

[14] Gao L M.  Existence of multiple solutions for a second-order difference equation with a parameter.Appl Math Comput, 2010, 216: 1592--1598

[15] Ding L, Tang C L. Positive solutions for critical quasilinear elliptic  equations with mixed Dirichlet-Neumann boundary conditions,Acta Mathematica Scientia, 2013, 33(2): 443--470