Groupoids and the associative law VIIA. (SH-groupoids of type (A, B, A) and their semigroup distances) Milan Trch (2007) Acta Universitatis Carolinae. Mathematica et Physica Similarity:
Grupoids and the associative law VII B (SH-grupoids and simply generated congruences) Milan Trch (2011) Acta Universitatis Carolinae. Mathematica et Physica Similarity:
Groupoids and the associative law III. (Szász-Hájek groupoids) Tomáš Kepka, Milan Trch (1995) Acta Universitatis Carolinae. Mathematica et Physica Similarity: