Direct Measurements of Smartphone Screen-Time: Relationships with Demographics and Sleep Christensen, Matthew A. ; Bettencourt, Laura ; Kaye, Leanne ; Moturu, Sai T. ; Nguyen, Kaylin T. ; Olgin, Jeffrey E. ; Pletcher, Mark J. ; Marcus, Gregory M. Abstract Publication: PLoS ONE Pub Date: November 2016 DOI: 10.1371/journal.pone.0165331 Bibcode: 2016PLoSO..1165331C