“…20,31,27 In recent years a posteriori error analysis and optimality investigations of steady-state adaptive discretizations have been widely tackled for several discretization approaches and model equations, obtaining several interesting results. 32,43,36,26 A large effort has been recently spent on unsteady problems, 47,4,23,37 as well as on other interesting issues like, for example, the analysis of stopping criteria during adaptive iterations. 40 Discretization approaches based on traditional simplicial elements are subject to many constraints when mesh refinement and coarsening are applied.…”