  This paper is a synthesis and extension of three earlier papers on
$PD_4$-complexes $X$ with fundamental group $\pi$ such that $c.d.\pi=2$ and
$\pi$ has one end. Our goal is to show that the homotopy types of such
complexes are determined by $\pi$, the Stiefel-Whitney classes and the
equivariant intersection pairing on $\pi_2(X)$. We achieve this under further
conditions on $\pi$.
