 Meanwhile, Hilbert and Klein undertook detailed investigations concerning the role of general covariance in theories of gravitation, and enlisted the assistance of Noether in their debate over the status of energy conservation in such theories. This led to Noether’s famous 1918 paper containing two theorems, the first of which leads to a connection between global symmetries and conservation laws, and the second of which leads to a number of results associated with local symmetries, including a demonstration of the different status of the conservation laws when the global symmetry group is a subgroup of some local symmetry group of the theory in question (see Brading and Brown, 2003).