title: Marijuana use among Calgary youths as a function of sampling and locus of control.
mesh_terms: D000293:Adolescent; D000328:Adult; D002170:Canada; D002188:Cannabis; D004522:Educational Status; D005260:Female; D006801:Humans; D007389:Internal-External Control; D008297:Male; D012494:Sampling Studies; D019966:Substance-Related Disorders