U.H. Gerlach (1968). "Derivation of the Ten Einstein Field Equations from the Semiclassical Approximation to Quantum Geometrodynamics". Physical Review. 177 (5): 1929–1941. Bibcode:1969PhRv..177.1929G. doi:10.1103/PhysRev.177.1929.
U.H. Gerlach (1968). "Derivation of the Ten Einstein Field Equations from the Semiclassical Approximation to Quantum Geometrodynamics". Physical Review. 177 (5): 1929–1941. Bibcode:1969PhRv..177.1929G. doi:10.1103/PhysRev.177.1929.