A comparative clinical study of doxophylline and theophylline on chronic obstructive pulmonary disease
LI Qian， LIU Yunqiu*， LAN Xuan， LIU Xiaoyu
Journal of Hebei Medical University . 2017, (12): 1376 -1380 .  DOI: 10.3969/j.issn.10073205.2017.12.004