Strong and Ordinary d-Algebras. - Jeong Soon Han; Hee Sik Kim; Joseph Neggers (J. Multiple Valued Log. Soft Comput., 2010)

The Hypergroupoid Semigroups as Generalizations of the Groupoid Semigroups. - Jeong Soon Han; Hee Sik Kim; Joseph Neggers (J. Appl. Math., 2012)

On linear fuzzifications of groupoids with special emphasis on BCK-algebras. - Jeong Soon Han; Hee Sik Kim; Joseph Neggers (J. Intell. Fuzzy Syst., 2013)