Mongkol, Sarayoot, Jirawan Chutubtim, Budsakorn Phonsean, Sutarat Kumbunkaed, Napaporn Vaewthong, and Thidarat Kawpil. 2018. “The Correlation Between Pulmonary Function and Six Minute Walk Distance in Male Patient With Chronic Obstructive Pulmonary Disease”. Archives of Allied Health Sciences 29 (3). Khon Kaen, Thailand:369-78. https://he01.tci-thaijo.org/index.php/ams/article/view/116083.