The Eigenvalue Problem For Arbitrary Matrices
Heinz Rutishauser · Birkhäuser Boston eBooks · 1990
The determination of the eigenvalues of nonsymmetric matrices is much more difficult, if for no other reason than the fact that for such matrices a concept analogous to the quadratic form is missing, and consequently, there are no extremal properties either. In accordance with these facts, the statement that eigenvalues are changed only a little by small perturbations in the matrix elements is also no longer valid.