Noninvasive mechanical ventilation in the weaning of patients with respiratory failure due to chronic obstructive pulmonary disease. A randomised, controlled trial. - Nava,S.; Ambrosino,N.; Clini,E.; Prato,M.; Orlando,G.; Vitacca,M.; Brigada,P.; Fracchia,C.; Rubini,F. (Ann Int Med, 1998)