On the partitioned matrix $\begin{pmatrix}O&A\\A^\ast &Q\\ \end{pmatrix}$ and its associated system $AX=T,A^\ast Y+QX = Z$Vladimiro ValerioRAIRO. Anal. numér., 15 2 (1981) 177-184DOI: https://doi.org/10.1051/m2an/1981150201771
