Buranapuntalug, S., W. Jalayondeja, and R. Chaunchaiyakul. “Effectiveness of Respiratory Resistance Training Device on Respiratory Muscles Strength and Endurance”. Archives of Allied Health Sciences, vol. 25, no. 2, Sept. 2013, pp. 181-92, https://he01.tci-thaijo.org/index.php/ams/article/view/66305.