Symmetries of the Kadomstev-Petviashvili Hierarchy
  The relation between the $\widehat{\Sl}(\infty)$ algebra of flows commuting with the KP hierarchy and the Kac-Moody-Virasoro Lie point symmetries of individual equations is established. This is used to calculate the point symmetries for all equations in the hierarchy. 
A. Yu. Orlov and P. Winternitz