Ge, B., and S. Heidarkhani. “Critical Points Approaches to Elliptic Problems Driven by a p(x)-Laplacian”. Ukrains’kyi Matematychnyi Zhurnal, vol. 66, no. 12, Dec. 2014, pp. 1676-93, https://umj.imath.kiev.ua/index.php/umj/article/view/2254.