Further Study on the Conservation Laws of Energy-momentum Tensor Density   for a Gravitational System
  The various methods to derive Einstein conservation laws and the relevant definitions of energy-momentum tensor density for gravitational fields are studied in greater detail. It is shown that these methods are all equivalent. The study on the identical and different characteristics between Lorentz and Levi-Civita conservation laws and Einstein conservation laws is thoroughly explored. Whether gravitational waves carry the energy-momentum is discussed and some new interpretations for the energy exchanges in the gravitational systems are given. The viewpoint that PSR1913 does not verify the gravitational radiation is confirmed. 
Chen Fang-Pei