The N-body Problem in Tetrad Gravity: a First Step towards the Unified   Description of the Four Interactions
  After a review of the canonical reduction to the rest-frame Wigner-covariant instant form of standard theories in Minkowski spacetime, a new formulation of tetrad gravity is introduced. Its canonical reduction, also in presence of N scalar particles, is done. The modification of the ADM formulation to solve the deparametrization problem of general relativity (how to recover the rest-frame instant form for G=0), is presented. 
L.Lusanna (Sezione INFN di Firenze, Italy)