Addiction and Engagement: An Explorative Study Toward Classification Criteria for Internet Gaming Disorder. - Mario Lehenbauer-Baum; Armin Klaps; Zuzana Kovacovsky; Karolin Witzmann; Raphaela Zahlbruckner; Birgit U. Stetina (Cyberpsychology Behav. Soc. Netw., 2015)