Ordóñez Iriarte, J. M., M. I. Aparicio Madre, J. J. Guillén Pérez, and M. J. Martínez García. “Low Blood Lead Levels and Educational Achievement in 7-8 Year Old Children in the Community of Madrid (Spain)”. Spanish Journal of Environmental Health, vol. 13, no. 1, June 2013, pp. 12-21, https://www.ojs.diffundit.com/index.php/rsa/article/view/281.