Clinical characteristics of patients with chronic obstructive pulmonary disease assessed using GOLD 2016 and GOLD 2018 classifications: a cross-sectional study in China

Wenhua Jian, Huiqing Zeng, Xiaoju Zhang, Chunmei Yun, Zuojun Xu, Yan Chen, Guochao Shi, Yingyu Wang, Yun Li, Jinping Zheng