  We briefly review of the definitions of the total energy, the total linear
momentum and the angular momentum of gravitational field when the cosmological
constant is zero. In particular, we show pseudo-tensor's definition of the
energy and the momentum given by Prof. Duan in 1963 agree with the ADM total
energy-momentum and the Bondi energy-momentum at spatial and null infinity
respectively. We also review the relevant energy-momentum inequalities.
Finally, we provide a short review of the positive energy theorem and the
peeling property of the Newmann-Penrose quantities when the cosmological
constant is positive.
