1. Einstein Manifolds;Besse,1987
2. Necessary and sufficient conditions for the existence of metrics in two-dimensional affine manifolds;Cheng;Chinese J. Phys.,1978
3. Necessary and sufficient conditions for the existence of metrics in three-dimensional affine manifolds;Cheng;Chinese J. Phys.,1979
4. Conditions for the local existence of a metric in a generic affine manifold;Cheng,1980
5. Sufficient conditions for a curvature tensor to be Riemannian and for determining its metric;Edgar;J. Math. Phys.,1991