  In this paper we compute the Emptiness Formation Probability of a (twisted-)
periodic XXZ spin chain of finite length at $\Delta=-1/2$, thus proving the
formulae conjectured by Razumov and Stroganov \cite{raz-strog1, raz-strog2}.
The result is obtained by exploiting the fact that the ground state of the
inhomogeneous XXZ spin chain at $\Delta=-1/2$ satisfies a set of qKZ equations
associated to $\displaystyle{U_q(\hat{sl_2})}$.
