Characteristics and correlates of electronic cigarette product attributes and undesirable events during e-cigarette use in six countries of the EUREST-PLUS ITC Europe Surveys - Kyriakos, CN; Filippidis, FT; Hitchman, S; Girvalaki, C; Tzavara, C; Demjen, T; Fernandez, E; Mons, U; Trofor, A; Tountas, Y; Zatonski, M; Zatonski, WA; et al. (Tobacco Induced Diseases, 2018)