The FourDimensionality of Space and the Einstein Tensor
Abstract
All tensors of contravariant valency two, which are divergence free on one index and which are concomitants of the metric tensor, together with its first two derivatives, are constructed in the fourdimensional case. The Einstein and metric tensors are the only possibilities.
 Publication:

Journal of Mathematical Physics
 Pub Date:
 June 1972
 DOI:
 10.1063/1.1666069
 Bibcode:
 1972JMP....13..874L