- Correspondence to Dr Huan-Zhong Shi, Department of Respiratory and Critical Care Medicine, Beijing Chaoyang Hospital, Capital Medical University, 8 Gongti Nanlu, Chaoyang District, Beijing 100020, China;
- Received November 12, 2016
- Revised July 12, 2017
- Accepted July 31, 2017
- First published August 26, 2017.
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