Szymczak, Arkadiusz, et al. “Petri Nets Modeling of Dead-End Refinement Problems in a 3D Anisotropic Hp-Adaptive Finite Element Method”. COMPUTING AND INFORMATICS, vol. 34, no. 2, Oct. 2015, pp. 425-57, https://www.cai.sk/ojs/index.php/cai/article/view/1839.