An identification theorem for $PSU_6(2)$ and its automorphism groups
  We identify the groups $PSU_6(2)$, $PSU_6(2):2$, $PSU_6(2):3$ and $Aut(PSU_6(2))$ from the structure of the centralizer of an element of order 3. 
Chris Parker and Gernot Stroth
math.GR