In Chap. we raise an open question from numerical analysis. Some progress due to the interplay of theory of nonlinear partial differential equations, combustion theory, and theory of numerical analysis will be expected in future (Minamoto–Yamamoto–Nakao (2000)). In particular, we leave the numerical analysis of the critical values \(\mu _{I}(a)\) and \(\mu _{E}(a)\) in the general case where \(0 \leq m < 1\) and \(0 \leq a(x^{\prime }) \leq 1\) on the boundary \(\partial D\) for future study (see Table 17.1).