Sawangjaithum, K., B. Hancharoenkul, S. Mongkol, U. Kamsrijai, and S. Kitchanapaiboon. “Comparison of respiratory muscle strength between cigarettes smokers, second-hand smokers and non-cigarettes smokers”. Journal of Associated Medical Sciences, vol. 50, no. 1, Jan. 2017, p. 132, https://he01.tci-thaijo.org/index.php/bulletinAMS/article/view/74525.