Multicenter Study

Severe COPD cases from Korea, Poland, and USA have substantial differences in respiratory symptoms and other respiratory illnesses.

Int J Chron Obstruct Pulmon Dis. 2017 Jan 1; 12: 3415-3423.
Observational Study

Characteristics and self-rated health of overlap syndrome.

Int J Chron Obstruct Pulmon Dis. 2014 Jan 1;9:795-804.
Multicenter Study

Socioeconomic status and COPD among low- and middle-income countries.

Int J Chron Obstruct Pulmon Dis. 2016 Jan 1; 11: 2497-2507.