Existence of a nontrivial solution for Choquard's equation

In this article, the authors consider the existence of a nontrivial solution for the following equation: -Delta u + u = q(x)(\u\(2) * 1/\x\)u, x is an element of R-3, where q(x) satisfies some conditions. Using a Min-Max method, the authors prove that there is at least one nontrivial solution for the above equation.