Krull dimension for limit groups III: Scott complexity and adjoining roots to finitely generated groups

This is the third paper in a sequence on Krull dimension for limit groups, answering a question of Z. Sela. We give generalizations of the well known fact that a nontrivial commutator in a free group is not a proper power to both graphs of free groups over cyclic subgroups and freely decomposable groups. None of the paper is specifically about limit groups.