Echinacea Reduces Antibiotics by Preventing Respiratory Infections: A Meta-Analysis (ERA-PRIMA) oleh Giuseppe Gancitano, Nicola Mucci, Rainer Stange, Mercedes Ogal, Selvarani Vimalanathan, Mahfuza Sreya, Anthony Booker, Bushra Hadj-Cherif, Werner C. Albrich, Karin Woelkart-Ardjomand, Samo Kreft, Wim Vanden Berghe, Godehard Hoexter, Andreas Schapowal, Sebastian L. Johnston