1.

Beckenbach, E. F. and Bellman, R.: *Inequalities*, Springer-Verlag, Berlin–Göttingen–Heidelberg, 1961.

2.

Cormen, Th. H., Leiserson, C. E., and Rivest, R. L.: *Introduction to Algorithms*, MIT Press, Cambridge, MA, and Mc-Graw Hill Co., N.Y., 1990.

3.

Garey, M. R. and Johnson, D. S.: *Computers and Intractability: a Guide to the Theory of NPCompleteness*, W. F. Freeman, San Francisco, 1979.

4.

Khachiyan, L. G.: A Polynomial-Time Algorithm for Linear Programming, *Soviet Math. Dokl.*
**20** (1) (1979), pp. 191–194.

5.

Kolmogorov, A. N. and Fomin, S. V.: *Elements of the Theory of Functions and Functional Analysis*, Nauka Publ., Moscow, 1972 (in Russian).

6.

Kreinovich, V., Lakeyev, A. V., and Noskov, S. I.: Optimal Solution of Interval Linear Systems is Intractable (NP-Hard), *Interval Computations* 1 (1993), pp. 6–14.

7.

Kreinovich, V., Lakeyev, A. V., and Noskov, S. I.: Approximate Linear Algebra is Intractable, *Linear Algebra and its Applications*
**232** (1) (1996), pp. 45–54.

8.

Lakeyev, A. V. and Noskov, S. I.: A Description of the Set of Solutions of a Linear Equation with Interval Defined Operator and Right-Hand Side, *Russian Acad. Sci. Dokl. Math.*
**47** (3) (1993), pp. 518–523.

9.

Lakeyev, A.V. and Noskov, S. I.:On the Set of Solutions of the Linear Equationwith the Intervally Given Operator and the Right-Hand Side, *Siberian Math. J.*
**35** (5) (1994), pp. 1074–1084 (in Russian).

10.

Oettli, W. and Prager, W.: Compatibility of Approximate Solution of Linear Equations with Given Error Bounds for Coefficients and Right-Hand Sides, *Num. Math.*
**6** (1964), pp. 405–409.

11.

Poljak, S. and Rohn, J.: Checking Robust Non-Singularity is NP-Hard,*Mathematics of Control, Signals and Systems*
**6** (1993), pp. 1–9.

12.

Rohn, J.: Systems of Linear Interval Equations, *Linear Algebra and its Applications*
**126** (1989), pp. 39–78.

13.

Rohn, J. and Kreinovich, V.: Computing Exact Componentwise Bounds on Solutions of Linear Systems with Interval Data is NP-Hard, *SIAM J. Matrix Anal. Appl.*
**16** (2) (1995), pp. 415–420.

14.

Shary, S. P.: Optimal Solution of Interval Linear Algebraic Systems. I, *Interval Computations* 2 (1991), pp. 7–30.

15.

Shary, S. P.:A New Class of Algorithms forOptimal Solution of Interval Linear Systems, *Interval Computations* 2 (4) (1992), pp. 18–29.

16.

Shary, S. P.: Solving Interval Linear Systems with Nonnegative Matrices, in: Markov, S. M. (ed.), *Proc. of the Conference “Scientific Computation and Mathematical Modelling”*, DATECS Publishing, Sofia, 1993, 179–181.