Bautista Pérez, F. and Pérez de Merino, M.A. 2016. Prevalence of consumption of alcohol and tobacco in 7th and 9th grade students from public educational centers in San Salvador. Revista Científica Crea Ciencia. 10, 2 (Dec. 2016), 28–36. DOI:https://doi.org/10.5377/creaciencia.v10i2.6033.