1. Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease; updated 2019. Available from: http://www.goldcopd.org/. Accessed Nov 30, 2018
2. COPD in Japan: the Nippon COPD Epidemiology study
3. Standardisation of spirometry
4. Japanese Respiratory Society. Guideline of respiratory function tests—spirometry, flow-volume curve, diffusing capacity of the lung (in Japanese). Tokyo: Japanese Respiratory Society, 2004. Japanese.