1. Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management and prevention of chronic obstructive pulmonary disease. GOLD 2015.
2. Jeon CM, and Oh KO. Prevalence of chronic obstructive pulmonary disease among adults over 40 years old in Korea, 2009-2013. Public Health Weekly Report, KCDC 2015;8:334-6.
3. Symptoms and Quadriceps Fatigability after Walking and Cycling in Chronic Obstructive Pulmonary Disease
4. Kang JI, Jeong DK, and Choi H. The effect of fatigue of patients with chronic obstructive pulmonary disease on depression and the health-related quality of life. J Kor Phys Ther 2014;26:262-8.
5. Choi JC, and Han DU. The effects of quadriceps setting exercise and electrical stimulation on improvement of quadriceps muscle strength. J Kor Phys Ther 2001;13:273-80.