Zarco-Alpuente, A.; Ciudad-Fernández, V.; Ballester-Arnal, R.; Billieux, J.; Gil-Llario, M. D.; King, D. L.; Montoya-Castilla, I.; Samper, P.; Castro-Calvo, J. Problematic Internet Use Prior to and During the COVID-19 Pandemic. Cyberpsychology 2021, 15, Article 1.