1. Deneš, J., Keedwell, A.D.: Latin Squares and Their Applications. Akadémia Kiadó, Budapest (1974)
2. Holgate, P.: Groupoids satisfying a simple invertive law. Math Student. 61, No 1–4, 101–106 (1992)
3. Kazim, M.A., Naseeruddin, M.: On almost semigroups. Aligarh Bull. Math. 2, 1–7 (1972)
4. Protić, P.V., Stevanović, N.: On Abel-Grassmann’s groupoids (review). In: Proceedings of the mathematical conference in Pristina. 31–38 (1994)
5. Protić, P.V., Stevanović, N.: AG-test and some general properties of Abel-Grassmann’s groupoids. PU.M.A. 6, No. 4, 371–383 (1995)