KholyavkaO. T. “Hyperbolic Variational Inequality of the Third Order With Variable Exponent of Nonlinearity”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 4, Apr. 2014, pp. 518–530, http://umj.imath.kiev.ua/index.php/umj/article/view/2154.