BCK-algebras have several connections with other areas of
investigation, such as: lattice ordered groups, MV -algebras, Wajsberg alge-
bras, and implicative commutative semigroups. J. M. Font et al.([2]) have
discussed Wajsberg algebras which are term-equivalent to MV -algebras. D.
Mundici([12]) proved MV -algebras are categorically equivalent to bounded
commutative BCK-algebra, and J. Meng([10]) proved that implicative com-
mutative semigroups are equivalent to a class of BCK-algebras. G. Georgescu
and A. Iorgulescu([3]) introduced the notion of a pseudo BCK-algebra. Y. B.
Jun characterized pseudo BCK-algebras. He found conditions for a pseudo
BCK-algebra to be ^-semi-lattice ordered. Y. B. Jun, H.S. Kim, J. Neg-
gers([8]) introduced the notion of a pseudo d-algebra as a generalization of the
idea of a d-algebra.