Havik, Trude, and Sigrun Ertesvåg. “Systematic Review and Classification Of: Olweus Bullying Prevention Program (OBPP) – A School-Wide Program Against Bullying and Antisocial Behavior (2. Ed.)”. Ungsinn. Journal of Effective Interventions for Children and Adolescents, vol. 12, no. 1, May 2020, https://doi.org/10.7557/25.7584.