Barber, Richard. “Research and Extension to Promote the Sustainability of the Basic Gratns System in the Slopes in the Area of El Salvador”. Agronomía Mesoamericana 8, no. 2 (June 1, 2016): 159–164. Accessed July 17, 2024. https://revistas.ucr.ac.cr/index.php/agromeso/article/view/24716.