1. Series and parallel addition of matrices;Anderson;J. Math. Anal. Appl.,1969
2. Generalized Inverses;Ben-Israel,2003
3. Matrix Mathematics: Theory, Facts, and Formulas;Bernstein,2009
4. Best Approximation in Inner Product Spaces;Deutsch,2001
5. Distance and parallelism between flats;DuPré;Linear Algebra Appl.,1992