1. Department of Respiratory Medicine, Gansu Province People Hospital, Lanzhou, Gansu, PR China
2. Department of
Neurological Surgery, The Second People Hospital of Lanzhou City, Lanzhou, Gansu, PR China
3. Department of Internal
Medicine, The Xigu Hospital of Lanzhou City, Lanzhou, Gansu, PR China
4. Department of Medicine, Respiratory
Medicine Unit , Karolinska Institute, Stockholm, Sweden
5. Department of Pulmonary Medicine, University of Helsinki
and Helsinki University Hospital, Helsinki, Finland