1. Wang Guojun, Theory of Σ-(α-tautologies) in revised Kleene systems, Science in China, Ser. E, 1998, 4(2):188–195.
2. Wang Guojun, Non-classic Logic and Approximate Reasoning (in Chinese), Beijing: Science Press, 2000.
3. Wang Guojun, Wang Wei, Logic metric space, Acta Mathematica Sinica (in Chinese), 2001, 44(1): 159–168.
4. Rosser, J. B., Turquette, A. R., Many-Valued Logics, Amsterdam: North-Holland, 1952.
5. Pavelka, J., On fuzzy logic I, II, III, Zeitschr. f. Math. Logik u. Grundlagen d. Math., 1979, 25: 45–52, 119–134, 447–464.