Effectiveness of The Umbrella Collaboration Versus Traditional Umbrella Reviews for Evidence Synthesis in Health Care: Protocol for a Validation Study - Beltran Carrillo; Marta Rubinos-Cuadrado; Jazmin Parellada-Martin; Alejandra Palacios-López; Beltran Carrillo-Rubinos; Fernando Canillas-Del Rey; Juan Jose Baztán-Cortes; Javier Gómez-Pavon (JMIR Research Protocols)