[1] G. Grätzer: 
Universal Algebra. Van Nostrand 1968. 
MR 0248066[2] G. Szász: 
Introduction to lattice theory. Budapest 1963. 
MR 0166118[3] I. Chajda B. Zelinka: 
Lattices of tolerances. Časopis pro pěstování matematiky, 102 (1977). 
MR 0450152[4] I. Chajda B. Zelinka: Minimal tolerances on lattices. Czech. Math. J., to appear.
[5] I. Chajda B. Zelinka: 
Compatible relations on algebras. Časopis pro pěst. matem., 100 (1975), 355-360. 
MR 0389710[6] B. Zelinka: Tolarance in Algebraic Structures. Czech. Math. J., 20 (1970), 175-178.
[7] I. Chajda B. Zelinka J. Niederle: 
On Existence Conditions for Compatible Tolerances. Czech. Math. J., 26 (101), 1976, 304-311. 
MR 0401561