[1] T. D. Mai: Partitions and congruences in algebras. Archivum Math. (Brno) 10 (1974), I: 111-122, II: 169-172, III: 173-187, IV: 231-253.
[2] H. Draškovičová:
The lattice of partitions in a set. Acta Fac. Rer. Nat. Univ. Comen. Math. 24 (1970), 37-85.
MR 0297652
[3] O. Borůvka: The theory of partitions in a set. (in Czech). Publ. Fac. Sci. Univ. Brno, No. 278 (1946), 1-37.
[4] O. Borůvka: Foundations of the theory of groupoids and groups. Berlin 1974 (in German Berlin, 1960; in Czech Praha, 1962).