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. Online. 22 March 2026. Vol. 67, no. 1, pp. 53 - 68. [Accessed 25 July 2026]. DOI 10.12775/TMNA.2025.035.