Multiplicity of solutions for a pLaplacian equation with nonlinear boundary conditions

In this paper we use the three critical points theorem attributed to B. Ricceri in order to establish existence of three distinct solutions for the following boundary value problem: lt;br / gt; lt;br / gt; begin{eqnarray*} lt;br / gt; left{ begin{array}{ll} Delta_p u = a(x) |u|^{p2} u mbox{ in lt;br / gt; $Omega$,}\\ |nabla u|^{p2} nabla u . nu = lambda f(x,u) lt;br / gt; mbox{ on $partialOmega$.}end{array} right. lt;br / gt; end{eqnarray*}