1. Model Theory;Chang,1973
2. Entropy and energy measures of a fuzzy set;De Luca,1979
3. Nonstandard entropy and energy measures of a fuzzy set;Gerla;J. Math. Anal. Appl.,1984
4. L-fuzzy sets;Goguen;J. Math. Anal. Appl.,1976
5. Introduction to the Theory of Infinitesimals;Stroyan,1976