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[2] P. Hájek K. Bendová Z. Renc: The GUHA method and the three valued logic. Kybernetika 7 (1971), 13-21. MR 0324940

[3] P. Hájek T. Havránek: Mechanizing hypothesis formation - mathematical foundations for a general theory. Springer-Verlag, Berlin-Heidelberg-New York, 1978. MR 0501342

[4] P. Hájek T. Havránek: The GUHA method - its aims and techniques. Int. J. Man-Machine Studies 10 (1978), 3-22.

[5] P. Hájek T. Havránek: A theory of helpful quantifiers and its application to approaches to missing information in the GUHA method. (In preparation for Kybernetika.)

[6] P. Hájek I. Havel T. Havránek M. Chytil Z. Renc J. Rauch: Metoda GUHA. Dům techniky, České Budějovice, sec. ed. 1977.

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[8] W. Lipski: Information systems with incomplete information. Proceedings of the third international symposion on automata theory, languages and programs, S. Michaelson, R. Milner (eds.). University Press, Edinburgh 1976, 120-130.