Next-to-next-to-leading order relation between R(e(+)e(-)-> b(b)over-bar) and Gamma(s1)(b -> clv(1)) and precise determination of vertical bar V-cb vertical bar

We present the next-to-next-to-leading order relation between the moments o f the Upsilon system spectral density and the inclusive B-meson semileptoni c width. The perturbative series for the width as an explicit function of t he moments is well convergent in three consequent orders in the strong coup ling constant that provides solid and accurate theoretical estimate. As a r esult, the uncertainty of the value of [V-cb] Cabibbo-Kobayashi-Maskawa mat rix element is reduced. (C) 1998 Published by Elsevier Science B.V. All rig hts reserved.