1. A generalized inverse for matrices;Penrose,1951
2. Finite Element Solution of Boundary Value Problems;Axelsson,1984
3. Matrix Computations;Golub,1983
4. Methods of conjugate gradients for solving linear systems;Hestenes;J. Res. Natn. Bur. Stand.,1952
5. Spares linear least-squares problems;Ikramov,1985