References
- J. Algebra v.89 no.2 Polygroups derived from cogroups S. Comer
- Lectrue notes in Math., Universal Algenbra and Lattice Theory no.1004 Extensiton of polygroups by polygroups and their representations using color schemes S. Comer
- Prolegomena of hypergroup theory(second edition) P. Corsini;Aviani(ed.)
- Rivista Math. Pura Appl. v.8 Una nota sul cuore di un ipergruppo e sulla chiusura trasititive β* di β D. Freni
- J. Math. Pures Appl. v.49 no.9 Groupoides, demi-hypergroupes et hypergroupes M. Koskas
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$8^{iem)$ congress Math. Scandinaves Sur une generalization de la nontion de groupe F. Marty - Hyperstructures and their representatuions T. Vougouklis
- Proceedings of the Fourth Internatioal Congress on Algebraic Hyperstructures and Applications (AHA 1990) The Fundamental relation in hyperrings. The general hyperfield T. Vougiouklis