High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 - Barbuy, Beatriz Leonor Silveira; Muniz, L; Ortolani, S; Ernandes, H; Dias, B; Saviane, I; Kerber, L; Bica, E; Pérez-Villegas, A; Rossi, L; Held, E.V (Astronomy & Astrophysics, 2018)