1. L. A. Zadeh, The Concept of a Linguistic Variable and Its Applications to Approximate Reasonings [Russian translation], Mir, Moscow (1976).
2. C. V. Negoita and D. A. Ralescu, Applications of Fuzzy Sets to Control Problems, Wiley, New York (1975).
3. S. A. Orlovskii, Problems of Acceptance of Solutions Under Nonfuzzy Initial Information [in Russian], Nauka, Moscow (1981).
4. R. Rockafellar, Convex Analysis, Princeton Univ. Press (1970).
5. S. S. Kutateladze and A. M. Rubinov, The Minkowski Duality and Its Applications [in Russian], Nauka, Novosibirsk (1976).