$R_{had}$ at the $B$-factory
  A systematic theoretical evaluation of the cross section for hadron production in electron-positron collisions in the energy range just below the $B$ meson threshold is presented which includes charm and bottom mass effects and is accurate to order $\as^3$. The corresponding measurement in the energy region several $GeV$ above the threshold is also discussed. 
K.G.Chetyrkin and J.H. K\"uhn