[1] Chajda I.: Tolerance lattice of algebras with restricted similarity type. Acta Univ. Palacki. Olomuc., Fac. rer. nat., Math. 34 (1995), 59-62. MR 1447254 | Zbl 0854.08001

[2] Chajda I.: Algebraic Theory of Tolerance Relations. Monograph Series of Palacký University Olomouc, 1991. Zbl 0747.08001