1. Principles of Artifical Intelligence;Nilsson,1980
2. Fuzzy sets as a basis for a theory of possibility;Zadeh;Fuzzy Sets and Systems,1978
3. Tree searching, Part 1: Basic techniques;Williams;Byte Magazine,1981
4. Fuzzy sets;Zadeh;Inform. and Control,1965
5. Fuzzy Sets and Systems: Theory and Applications;Dubois,1980