  We consider the spectral function $\rho(\mu)$ $(\mu \geq 0)$ for the
Sturm-Liouville equation $y^{''}+(\lambda-q)y =0$ on $[0,\infty)$ with the
boundary condition $y(0)=0$ and where $q$ has slow decay $O(x^{-\alpha})$
$(a>0)$ as $x\to \infty$. We develop our previous methods of locating spectral
concentration for $q$ with rapid exponential decay (JCAM 81 (1997) 333-348) to
deal with the new theoretical and computational complexities which arise for
slow decay.
