Koolnapadol, N., S. Sripattanapipat, S. Skullong, P. Wiriyavitsajjar, W. Thungwinyoo, and C. Suppasubsiri. “Numerical Heat Transfer Study in a Round Tube With Inclined Rectangular Rings”. Journal of Research and Applications in Mechanical Engineering, vol. 4, no. 2, Aug. 2018, pp. 183-91, https://ph01.tci-thaijo.org/index.php/jrame/article/view/138662.