1. R. E. Moore, ?On computing the range of a rational function of n variables over a bounded region,? Computing,16, No. 1?2, 1?15 (1976).
2. Yu. I. Shokin, Interval Analysis [in Russian], Nauka, Novosibirsk (1981).
3. M. A. Frumkin, ?The complexity of discrete problems,? Preprint, Akad. Nauk SSSR, Tsentr. Ékon. Mat. Inst., Moscow (1981).
4. A. V. Aho, J. E. Hopcroft, and J. D. Ullman, The Design and Analysis of Computer Algorithms, Addison-Wesley, Reading, Mass. (1974).