  A coassociative Lie algebra is a Lie algebra equipped with a coassociative
coalgebra structure satisfying a compatibility condition. The enveloping
algebra of a coassociative Lie algebra can be viewed as a coalgebraic
deformation of the usual universal enveloping algebra of a Lie algebra. This
new enveloping algebra provides interesting examples of noncommutative and
noncocommutative Hopf algebras and leads to a classification of connected Hopf
algebras of Gelfand-Kirillov dimension four in [WZZ].
