Efficacy of a Self-Guided Internet Intervention With Optional On-Demand Feedback Versus Digital Psychoeducation on Sleep Hygiene for University Students With Insomnia: Randomized Controlled Trial. - Zarski AC; Bernstein K; Baumeister H; Lehr D; Wernicke S; Küchler AM; Kählke F; Spiegelhalder K; Ebert DD (Journal of medical Internet research, 2025)