The value of exhaled nitric oxide in different parts of the airway in chronic obstructive pulmonary dis⁃ ease 

WU min, JIN Mengmeng, ZHAO Lei.
The Journal of Practical Medicine . 2021, (9): 1145 -1149 .  DOI: 10.3969/j.issn.1006⁃5725.2021.09.010