A note on associative triples of elements in cancellation groupoids Tomáš Kepka (1980) Commentationes Mathematicae Universitatis Carolinae
A note on subdirectly irreducible groupoids Tomáš Kepka (1981) Acta Universitatis Carolinae. Mathematica et Physica
A note on the finite extensivity property Jarmila Fauknerová (1981) Commentationes Mathematicae Universitatis Carolinae