[1] Chajda I.: Lattices of compatible relations. Arch. Math. (Brno) 13 (1977), 89-96. MR 0463081 | Zbl 0372.08002

[2] Chajda I., Zelinka В.: Lattices of tolerances. Čas. pěst. mat. 102 (1977), 10-24. MR 0450152 | Zbl 0354.08011

[3] Chajda I., Nieminen J.: Atomicity of tolerance lattices. Czech. Math. J. 30 (1980), 606 to 609. MR 0592323 | Zbl 0467.06006

[4] Clifford A. H., Preston G. В.: The algebraic theory of semigroups. Amer. Math. Soc., Providence, R. I. Vol. I (1961); Vol. II (1967). Zbl 0111.03403

[5] Zelinka В.: Tolerance in algebraic structures II. Czech. Math. J. 25 (1975), 175-178. MR 0457323 | Zbl 0316.08001

[6] Pondělíček В.: On tolerances on periodic semigroups. Czech. Math. J. 28 (1978), 647-649. MR 0498924