An In-Person and Online Intervention for Parkinson Disease (UPGRADE-PD): Protocol for a Patient-Centered and Culturally Tailored 3-Arm Crossover Trial - Michail Elpidoforou; Irene Grimani; Marianna Papadopoulou; Nikolaos Papagiannakis; Anastasia Bougea; Athina-Maria Simitsi; Evangelos Sfikas; Ioanna Alexandratou; Ioanna Alefanti; Roubina Antonelou; Christos Koros; Ioanna Mavroyianni; et al. (JMIR Research Protocols)