1. Institute of Biomedical Research (IIB Sant Pau); Iberoamerican Cochrane Centre; Sant Antoni Maria Claret 171 Edifici Casa de Convalescència Barcelona Catalonia Spain 08041
2. CIBER Epidemiología y Salud Pública (CIBERESP), Spain; Iberoamerican Cochrane Centre - IIB Sant Pau; c/ Sant Antoni Maria Claret 171 Barcelona Spain 08041
3. Washington Hospital Center; Georgetown University Medical Center; 110 Irving Street, NW Washington DC USA 20010