Building a Digital Health Research Platform to Enable Recruitment, Enrollment, Data Collection, and Follow-Up for a Highly Diverse Longitudinal US Cohort of 1 Million People in the All of Us Research Program: Design and Implementation Study - Dave Klein; Aisha Montgomery; Mark Begale; Scott Sutherland; Sherilyn Sawyer; Jacob L McCauley; Letheshia Husbands; Deepti Joshi; Alan Ashbeck; Marcy Palmer; Praduman Jain (Journal of Medical Internet Research)