Factors Associated With the Utilization of Outpatient Virtual Clinics: Retrospective Observational Study Using Multilevel Analysis - Yun-Hsuan Tzeng; Wei-Hsian Yin; Kuan-Chia Lin; Jeng Wei; Hao-Ren Liou; Hung-Ju Sung; Hui-Chu Lang (Journal of Medical Internet Research, 2022)