  This paper proves that the imaginary part of the Riemann $\xi$ function is
strictly monotonic with $b$ in the region $S = \{t|t=a+bi,\ 0\leq a \leq
9.508,\ -1/2<b<1/2\}$. That leads to Im($\xi$)=0 being true only when $b=0$ in
$S$.
