Lingen Chen., Shaojun Xia., and Fengrui Sun. “Maximum Efficiency of an Irreversible Heat Engine With a Distributed Working Fluid and Linear Phenomenological Heat Transfer Law”. Revista Mexicana De Física, vol. 56, no. 3, Jan. 2010, pp. 231-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3754.