What are good books or articles about linear projectors in Hilbert spaces? I am mostly interested in the finite dimensional case (but anything is welcome).
All about idempotents, orthogonal and oblique projectors, partitions of identity, useful formulas, results, theorems...
Thanks!
(Feel free to modify tags appropriately.)
For finite-dimensional oblique projectors I'd recommend the Springer monograph Ben-Israel and Greville Generalized Inverses doi 10.1007/b97366