Tobacco use among working adolescents and high school students in Turkey: evaluating the effect of the national tobacco control policy - Erkan Çakır; Bülent Karadağ; Refika Ersu; Fazilet Karakoç; Nezih Varol; Ali Özdemir; Ahmet Hakan Gedik; Nazlı Karacabey; Hakan Yazan; Elif Dağlı (The Turkish Journal of Pediatrics)