1. La Princesa Hospital; Internal Medicine Department; Diego de León, 62 Madrid Spain 28006
2. Iberoamerican Cochrane Centre, Biomedical Research Institute Sant Pau (IIB Sant Pau), CIBER Epidemiología y Salud Pública (CIBERESP); Barcelona Spain
3. 12 de Octubre Hospital; Intensive Care Department; Avda de Cordoba, s/n, 28041 Madrid Spain
4. Hospital Universitario Ramón y Cajal (IRYCIS). CIBER Epidemiology and Public Health (CIBERESP); Clinical Biostatistics Unit; Carretera de Colmenar Km 9.100 Madrid Spain 28034
5. 12 de Octubre Hospital; Medical Library; Avd de Córdoba s/n Madrid Spain 28041
6. Hospital Universitario Príncipe de Asturias. CIBER Epidemiology and Public Health (CIBERESP); Department of Preventive Medicine and Public Health; Ctra. Alcalá-Meco s/n Alcalá de Henares Madrid Madrid Spain 28805