Orpel, Aleksandra. “Sufficient and Necessary Conditions for the Existence of Positive Solutions With Finite Energy for Elliptic Systems in Exterior Domains”. Topological Methods in Nonlinear Analysis 67, no. 1 (March 22, 2026): 53–68. Accessed July 25, 2026. https://apcz.umk.pl/TMNA/article/view/70080.