[1] W. Belousov: Introduction in the theory of quasigroups and loops. Moscow (1967), (in Russian).

[2] J. Dudek: The number of algebraic operations in an idempotent groupoid. Cooloq. Math. 21. (1970), 169-177. DOI 10.4064/cm-21-2-169-177 | MR 0263959

[3] J. Dudek: Medial groupoids and Mersenne numbers. to appear in Fund. Math. MR 0643550 | Zbl 0478.08012

[4] T. Evans: Products of points - some simple algebras and their identities. Amer. Math. Monthly Vol. 74, no 4. April, 1967. MR 0209382 | Zbl 0207.32901

[5] G. Gratzer: Universal Algebra. D. von Norstrand Company, 1968. MR 0248066

[6] J. Ježek, T. Kepka: The lattice of varieties of commutative abelian distributive groupoids. Algebra Univ. 5 (1975) 225-237. MR 0398952

[7] N. Kimura, M. Yamada: Note on idempotent semigroups II. Proc. of Jap. Acad., 34 (1958), 110-112. DOI 10.3792/pja/1195524790 | MR 0098141 | Zbl 0081.25501

[8] A. Kisielewicz: The number of algebraic operations in idempotent algebras. to appear in Algebra Univ.

[9] E. Marczewski: Independence and homomorphisms in abstract algebras. Fund. Math. 50 (1961), 45-61. DOI 10.4064/fm-50-1-45-61 | MR 0138572 | Zbl 0104.25501

[10] A. Mitsche, H. Werner: On groupoids representable by linear spaces over finite fields. Arch. Math. Vol. 24 (1973), 14-20. DOI 10.1007/BF01228164 | MR 0316601

[11] J. Plonka: Diagonal algebras. Fund. Math. 50 (1966), 309-321. DOI 10.4064/fm-58-3-309-322 | MR 0194378 | Zbl 0166.27501

[12] J. Plonka: On algebras with n district essentially n-ary operations. Algebra Univ. (1971), 73-74. MR 0286928

[13] J. Plonka: On functionally uniform symmetrical algebras. Colloq. Math. 15 (1966), 181 to 187. DOI 10.4064/cm-15-2-181-188 | MR 0205904 | Zbl 0146.25102

[14] J. Soublin: Etude algébrique de la notion de moyenne. J. Math. Pures et App. 50 (1977), 53-264.