  In this paper we investigate the structure of the glue in Zwanziger's gauge
invariant expansion for the A^2-type mass term in Yang-Mills theory. We show
how to derive this expansion, in terms of the inverse covariant Laplacian, and
extend it to higher orders. In particular, we give an explicit expression, for
the first time, for the next to next to leading order term. We further show
that the expansion is not unique and give examples of the resulting ambiguity.
