  Foreword. While most textbooks of general relativity and research articles
discuss at length the relative merits of the pseudo tensors proposed by
Einstein and by other authors for representing the energy of the gravitational
field, Levi Civita's definition of a true gravitational energy tensor has
succumbed to the authority of Einstein and is nearly forgotten. It seems
however worthy of a careful re-examination, due to its unquestionable logical
soundness and to the unique manner of propagation for gravitational energy that
it entails.
