Spherical Gravitational Waves in Relativistic Theory of Gravitation
  Within the framework of relativistic theory of gravitation the exact spherically-symmetric wave solution is received. It is shown that this solution possesses the positive-definite energy and momentum deriving with the Fock energy-momentum density tensor of gravitational field. In this connection the sense of Birkhoff theorem in Relativistic Theory of Gravitation is discussed. 
A.A. Leonovich, Yu.P. Vyblyi
physics.gen-ph