“…Consider the CALE (1) with: Then, the unique positive definite solution of (1) is: With \documentclass{article} \footskip=0pc\pagestyle{empty} \begin{document} $\alpha\,{=}\,1$ \end{document}, the lower matrix bounds for the solution P are found by Theorems 2.1 and 2.3, respectively, to be In fact, it can be seen that \documentclass{article} \footskip=0pc\pagestyle{empty} \begin{document} $P_{L2}\,{=}\,P_{exact}$ \end{document}. Since Q is singular, the matrix bounds proposed in 3, 6–8, 10–12, 14, 16, 17 cannot work here. The lower bound P L 11 gives the trivial bound P ≥0.…”