Infinitely small transformations preserving the curvature of a Riemannian space

The necessary and sufficient conditions for tensor character are obtained, for which an infinitely small transformation of the space $V_n4 preserves its Riemannian curvature for any two-dimensional area. It is proved that for$n>3$ the subprojective spaces of the exceptional case, satisfying a certain condition, and only they, permit nontrivial, infinitely small conformal transformations preserving the Riemannian curvature of each two-dimensional area.