“…Alves [1], Ma-Rivera [14] and HeZou [11] studied the existence of positive solutions and infinitely many positive solutions of the problem (1.3) by variational methods, respectively; Perera and Zhang [17] obtained one nontrivial solutions of (1.3) by Yang index theory; Mao-Zhang [15], Zhang and Perera [20] got three nontrivial solutions (a positive solution, a negative solution, a sign changing solution) of (1.3) by invariant sets of descent flow; Cheng-Wu [6] obtained the existence results of positive solutions of problem (1.3), also in [7] they used a three critical point theorem due to Brezis-Nirenberg [4] and a Z 2 version of the Mountain Pass Theorem due to Rabinowitz [19] to study the existence of multiple nontrivial solutions of problem (1.3) under some weaker assumptions. In order to establish multiple solutions for problem (1.1), we make the following assumptions:…”