Association of Electronic Cigarette Usage with the Subsequent Initiation of Combustible Cigarette Smoking among Dental Students in Riyadh, Saudi Arabia: A Longitudinal Study oleh Sanjeev B. Khanagar, Ibrahim Aldawas, Salman Khalid Alrusaini, Farraj Albalawi, Aram Alshehri, Mohammed Awawdeh, Kiran Iyer, Darshan Devang Divakar