Rika Alamsyah, Lina Natamiharja, and Rizka Handayani, “HUBUNGAN KEBIASAAN MEROKOK DENGAN STATUS PERIODONTAL TUKANG BECAK DI SEKITAR KAMPUS USU MEDAN: RELATIONSHIP BETWEEN SMOKING AND PERIODONTAL STATUS OF PEDICAP RIDER AROUND USU CAMPUS MEDAN”, Dentika Dental J., vol. 17, no. 2, pp. 128 - 133, Dec. 2012.