follow closely the derivation given in Ref. [@mandel95]. Our starting point is the following algebraic inequality $$-1 \le xy-xy'+x'y+x'y'-x'-y \le 0 \; 
\label{Clauser}$$ which holds for any variable $0 \le x,y,x',y' \le 1$. Let us now introduce explicitly a set of hidden variables $\tau$ which take values in a space ${\cal T}$. We assume that the incoming entangled electron states are described by $\tau$ in all the details necessary to determine the probability distributions $P(Q_{\alpha},\tau)$ for transferring a number of $Q_{\alpha}$ electronic charges into lead $\alpha=1,2$. By imposing that the hidden variable theory is local, it follows that the joint probability can be expressed in the following form: $$P(Q_1,Q_2)= \int_{\cal T} {\cal M}(\tau) P(Q_1,\tau) P(Q_2,\tau) d \tau ,
\label{jpd1}$$ where ${\cal M}(\tau)d\tau$ defines a probability measure on the space ${\cal T}$. The physical meaning of Eq.(\[jpd1\]) is straightforward: it states that the probability distribution on lead ${\alpha}$ does not depend on the probability distribution on the lead ${\beta}$.

We now introduce $P^{\theta_1,\theta_2}(Q_1,Q_2)$ as the joint probability for transferring $Q_1$ and $Q_2$ electronic charges when both analyzers are present, while $P^{\theta_1,-}(Q_1,Q_2)$ and $P^{-,\theta_2}(Q_1,Q_2)$ are the corresponding joint probabilities when one of the two analyzers is removed. If the condition $$P^{\theta_\alpha}(Q_\alpha,\tau) \le 