Define Mn to be the set of
equivariant, unoriented cobordism classes of n-dimensional 2-torus manifolds, where
any such manifold is smooth, closed and n-dimensional, and has an effective
smooth action of a rank n 2-torus group (ℤ2)n. Then Mn forms an abelian
group with respect to disjoint union. For n = 3, we determine the group
structure of Mn and show that each class of Mn contains a small cover as its
representative.