Kalita E. A. “Properties of Solutions of Half-Linear Elliptical Systems of Nondivirgent Kind”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 2 (February 28, 1992): 184-191. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/7831.