[1] J. JEŽEK T. KEPKA: 
Distributive groupoids and symmetry-by-mediality. (to appear). 
MR 0758318[2] J. JEŽEK T. KEPKA P. NĚMEC: 
Distributive groupoids. Rozpravy ČSAV, Řada Mat. a Přír. Věd, 91/3 (1981), 1-94. 
MR 0672563[4] T. KEPKA: 
Distributive groupoids and preradicals, I. Comment. Math. Univ. Carolinae 24 (1983), 183-197. 
MR 0703936 | 
Zbl 0519.20055[5] T. KEPKA: 
Distributive groupoids and preradicals, II. Comment. Math. Univ. Carolinae 24 (1983), 199-209. 
MR 0711258 | 
Zbl 0529.20057[6] T. KEPKA P. NĚMEC: 
Distributive groupoids and the finite basis property. J. of Algebra 70 (1981), 229-237. 
MR 0618390[7] J. P. SOUBLIN: 
Étude algébrique de la notion de moyenne. J. Math. Pures et Appl. 50 (1971), 53-264. 
MR 0291342 | 
Zbl 0215.40401