Effects of a Combination of Elderberry and Reishi Extracts on the Duration and Severity of Respiratory Tract Infections in Elderly Subjects: A Randomized Controlled Trial oleh Carlos Gracián-Alcaide, Jose A. Maldonado-Lobón, Elisabeth Ortiz-Tikkakoski, Alejandro Gómez-Vilchez, Juristo Fonollá, Jose L. López-Larramendi, Mónica Olivares, Ruth Blanco-Rojo