Kowalczyk, A., O. Dąbska, M. Warchoł, and R. Gotowski. “Drug Addiction Problem in Poland in Relation to International Comparisons”. Journal of Education, Health and Sport, vol. 7, no. 5, May 2017, pp. 766-80, https://apcz.umk.pl/JEHS/article/view/4663.