Constraints of the fourth generation from $g_\mu -2$
  We investigate the newly observed muon $g_\mu -2$ anomaly in the framework of a sequential fourth generation model with a heavy fourth neutrino, $\nu'$. We find that $g_\mu -2$ can exclude most values of $m_{\nu'}$ and put a very stringent constraint on the existence of the fourth generation. We also obtain bounds of a $4\times 4$ leptonic mixing matrix elements, $V_{2\nu'}$ if it really exists. 
W.J. Huo and T.F. Feng (IHEP, Cas)