The gravitational field energy momentum tensor in the Einstein equation. Construction of the gravitational field equation

Einstein, when he began working on the general theory of relativity, believed that energy of any kind is the source of the gravitational field. Therefore, the energy of gravity, like any energy, must be the source of the field. It was previously discovered that the energy-momentum tensor of the gravitational field is already contained in the Ricci tensor. This hypothesis is used to construct a new equation of the gravitational field.