The Moore-Penrose inverse of a partitioned matrix $M=\begin{pmatrix} A & 0 \\ B & C \end{pmatrix}$.
(English).Czechoslovak Mathematical Journal,
vol. 25
(1975),
issue 3,
pp. 354-361
[3] Meyer Carl: Generalized Inverse of Triangular Matrices. SIAM J. Appl. Math. 18 (1970), 401-406. DOI 10.1137/0118034 | MR 0257100
[4] Rao С. R., S. K. Mitra: Generalized Inverse of Matrices and its Applications. John Wiley and Sons, Inc., New York, 1971, pp. 21, 67. MR 0338013 | Zbl 0236.15005