Text Messaging Versus Postal Reminders to Improve Participation in a Colorectal Cancer Screening Program: Randomized Controlled Trial - Nuria Vives; Gemma Binefa; Noemie Travier; Albert Farre; Jon Aritz Panera; Berta Casas; Carmen Vidal; Gemma Ibáñez-Sanz; Montse Garcia (JMIR mHealth and uHealth)