Invariant prolongation of overdetermined PDE's in projective, conformal   and Grassmannian geometry
  This is the second in a series of papers on natural modification of the normal tractor connection in a parabolic geometry, which naturally prolongs an underlying overdetermined system of invariant differential equations. We give a short review of the general procedure developed in [5] and then compute the prolongation covariant derivatives for a number of interesting examples in projective, conformal and Grassmannian geometries. 
Matthias Hammerl, Petr Somberg, Vladim\'ir Sou\v{c}ek, Josef   \v{S}ilhan
math.DG math.AP