Cohomology of the variational bicomplex on the infinite order jet space
  We obtain the cohomology of the variational bicomplex on the infinite order jet space of a smooth fiber bundle in the class of exterior forms of finite jet order. This provides a solution of the global inverse problem of the calculus of variations of finite order on fiber bundles. 
G.Giachetta, L.Mangiarotti and G.Sardanashvily