1. E. Zieman and O. B’yuneman, “Tolerant Spaces and Brain,” in: Na Puti k Teoreticheskoi Biologii, Mir, Moscow (1970), pp. 52–68.
2. Yu. A. Shreider, Equality, Similarity, and Order [in Russian], Mir, Moscow (1971).
3. Yu. A. Shreider, “Tolerance spaces,” Cybernetics, No. 2, 124–128 (1970).
4. S. M. Yakubovich, “Axiomatic similarity theory,” NTI, Ser. 2, No. 10, 15–19 (1968).
5. S. N. Gerasin, E. V. Sklyar, and V. V. Shlyakhov, “A property of tolerance relation,” Dop. NAN Ukr., No. 12, 58–62 (2003).