“…example, [21][22][23][24][25]). Several specific estimates, such as the adjoint-weighted residual method [17,20], the energy norm based estimates [26], the Green's function decomposition method [27], the strict-bounding approach based on Lagrangian formulation [28], the CRE-based error estimation [25], have been proposed and applied in solutions of Poisson's equation, linear and non-linear static problems in solid mechanics, eigenvalue problems, time-dependent problems, non-trivial problems of CFD and etc [29,30]. Among the available techniques, the CRE-based error estimation is a one to guarantee strict bounds of quantities.…”