Li, G., and C. Wang. “The Existence of a Nontrivial Solution to a Nonlinear Elliptic Problem of Linking Type Without the Ambrosetti-Rabinowitz Condition”. Annales Fennici Mathematici, vol. 36, no. 2, Aug. 2011, pp. 461-80, doi:10.5186/aasfm.2011.3627.