B⁰ - bar{B}⁰ oscillations and measurements of |V_(ub)|/|V_(cb)| at LEP

In this paper a review of the LEP analyses on $B^0 - \bar{B}^0$ oscillations and on the measurement of $|V_{ub}|/|V_{cb}|$ is presented . These measurements are of fundamental importance in constraining the $\rho$ and $\eta$ parameters of the CKM matrix. A review of the current status of the $V_{CKM}$ matrix determination is also given.