De Morais DC, Souto MAS, do Ó JM. A compactness embedding lemma, a principle of symmetric criticality and applications to elliptic problems. Proyecciones (Antofagasta, On line) [Internet]. 2000May1 [cited 2024Apr.26];19(1):1-17. Available from: https://www.revistaproyecciones.cl/index.php/proyecciones/article/view/1627