“The Cadmium and Lead Levels in cow´s Milk Marketed in the City of Guayaquil, Ecuador”. Revista Científica Ciencias Naturales y Ambientales 8, no. 2 (January 5, 2015): 6. Accessed December 5, 2025. https://revistas.ug.edu.ec/index.php/cna/article/view/1743.