  In this paper, we study a particular case of Gorenstein projective,
injective, and flat modules, which we call, respectively, strongly Gorenstein
projective, injective, and flat modules. These last three modules give us a new
characterization of the first modules, and confirm that there is an analogy
between the notion of Gorenstein projective, injective, and flat modules and
the notion of the usual projective, injective, and flat modules.
