1. J. Ehlers, Konstruktionen und Charakterisierungen von Lösungen der Einsteinschen Gravitationsfeldgleichungen, Dissertation, Hamburg University, Hamburg, Germany (1957).
2. J. Ehlers, Transformation of static exterior solutions of Einstein’s gravitational field equations into different solutions by means of conformal mappings, in Les theories relativistes de la gravitation, Colloques Internationaux du CNRS 91 (1962).
3. R.P. Geroch, A method for generating solutions of Einstein’s equations, J. Math. Phys. 12 (1971) 918 [ INSPIRE ].
4. R.P. Geroch, A method for generating new solutions of Einstein’s equation. 2, J. Math. Phys. 13 (1972) 394 [ INSPIRE ].
5. E. Cremmer and B. Julia, The SO(8) supergravity, Nucl. Phys. B 159 (1979) 141 [ INSPIRE ].