Biedroń, N., M. Szabat, J. Dąbrowski, K. Dębek, and I. Gąbka. “The Relationship Between Internet Addiction and Mental Health Problems Such As Depression Symptoms, Anxiety and Insomnia before and During Covid-19 Pandemic”. Journal of Education, Health and Sport, vol. 11, no. 8, Aug. 2021, pp. 215-2, doi:10.12775/JEHS.2021.11.08.022.