Quasigroups which are unions of three proper subquasigroups Tomáš Kepka, D. Rosendorf (2004) Acta Universitatis Carolinae. Mathematica et Physica Similarity:
Notes on the number of associative triples Jaroslav Ježek, Tomáš Kepka (1990) Acta Universitatis Carolinae. Mathematica et Physica Similarity: