[1] R. Bek M. Růžička: 
On modelling of large variable systems of higher degree by means of language systems. Kybernetika 15 (1979), 6, 408-428. 
MR 0562373 
[2] R. Bek Z. Pokorný: 
Basic terms of the theory of compartmental systems. Kybernetika 17 (1981), 4, 338-347. 
MR 0643919 
[4] A. Kaufmann: 
Introduction to the Theory of Fuzzy Subsets. Academic Press, New York-San Francisco-London 1975. 
MR 0485402 | 
Zbl 0332.02063 
[5] W. Wechler: 
The Concept of Fuzziness in Automata and Language Theory. Akademie - Verlag, Berlin 1978. 
MR 0533359 | 
Zbl 0401.94048 
[6] L. A. Zadeh: 
Quantitative Fuzzy Semantics. Information Sciences 3, University of California, Berkley 1971. 
MR 0286607 | 
Zbl 0218.02057 
[7] A. Jirásek: Bolest se stanoviště moderního chirurga. Sbírka přednášek České akademie věd a umění, Praha 1938.