title: Marijuana use in urban secondary schools: a three-year comparison.
mesh_terms: D000293:Adolescent; D001741:Black or African American; D002188:Cannabis; D006801:Humans; D008800:Mexico / Q000208:ethnology; D012959:Socioeconomic Factors; D013334:Students; D019966:Substance-Related Disorders / Q000453:epidemiology*; D013781:Texas; D013997:Time Factors