Julia sets for certain rational functions (Q1099292)

Let R denote a rational function of the form \[ R(z)=az- \sum^{n}_{1}\{b_ i/(z-c_ i)\}, \] where \(a>1\), \(b_ i\geq 0\) and \(c_ 1<c_ 2<...<c_ n\). The Julia set J of R is a real Cantor set. The authors give upper and lower bounds for the Hausdorff dimension of J.