  Let G be a torsion--free abelian group of finite rank. The automorphism group
Aut(G) acts on the set of maximal independent subsets of G. The orbits of this
action are the isomorphism classes of indecomposable decompositions of G. G
contains a direct sum of strongly indecomposable groups as a characteristic
subgroup of finite index, giving rise to a classification of finite rank
strongly indecomposable torsion--free abelian groups.
