ECA: Estudios Centroamericanos. “La encíclica "Populorum Progessio" De Paulo IV”. ECA: Estudios Centroamericanos 22, no. 227 (June 30, 1967): 475–476. Accessed May 22, 2026. https://revistas.uca.edu.sv/index.php/eca/article/view/10535.