Fundamental Properties of Lagrangian Density for A Gravitational System   and Their Derivations
  Through the discussion of the fundamental properties of Lagrangian density for a gravitational system, the theoretical foundations of the modified Einstein field equations and the Lorentz and Levi-Civita conservation laws are systematically studied. Our study confirms the view that they could be used as the premises to establish a new cosmology. 
Fang-Pei Chen