This paper presents a class of limited memory preconditioners (LMPs) for solving linear systems of
equations with multiple nonsymmetric matrices and multiple right-hand sides. These preconditioners based
on limited memory quasi-Newton formulas require a small number k of linearly independent vectors.
They may be used to improve an existing first-level preconditioner and are especially worth considering
when the solution of a sequence of linear systems with slowly varying left-hand sides is addressed
