“The Effectiveness of Group Counseling Using the Behavior Contract Technique in Improving Vocational High School Students’ Discipline”, Hambaruan, vol. 1, no. 1, hlm. 16–26, Jun 2026, Diakses: 3 Juni 2026. [Daring]. Tersedia pada: https://abecen.com/index.php/Hambaruan/article/view/12