Hyperidentities of groups and semigroups. (Short Communication). George M. Bergman (1981) Aequationes mathematicae
Hyperstability of a class of linear functional equations. Maksa, Gyula, Páles, Zsolt (2001) Acta Mathematica Academiae Paedagogicae Nyí regyháziensis. New Series [electronic only]
Hyperstructures Associated with Ordered sets Piergiulio Corsini (2003) Δελτίο της Ελληνικής Μαθηματικής Εταιρίας