Matrix Li-Yau-Hamilton estimates for the heat equation on Kaehler   manifolds
  We proved a matrix Li-Yau-Hamilton type gradient estimates for the positive solutin of the heat equation on complete Kaehler manifolds with nonnegative bisectional curvature. As a consequence we obtain a comparison theorem for the distance function under this curvature assumption. 
Huai-dong Cao, Lei Ni