“…Since it may be expensive to work with (A-iJ 1)-1 (i.e., to solve equations as (A-{} I)z = r exactly) in each step, one might prefer suitable approximations K of A -{)I or of A -µI (preconditioners; cf. [5,8,17,18,20]). Then, in JD, the search subspace is expanded by some appropriate linear combination of K-1 (A -7'J I) u and K-1 u while the Shift-and-Invert Arnoldi, properly adapted, will expand by K-1 u only.…”