1. Kerr, R. P., and Schild, A. (1965). In Proceeding of the Galileo Galilei Centenary Meeting on General Relativity, Problems of Energy and Gravitational Waves, G. Barbera, ed., Comiato Nazionale per le Manifestazione Celebrative, Florence, pp. 222–233.
2. Trautman A. (1962). In Recent Developments on General Relativity (Pergamon Press, New York).
3. Kerr, R. P. (1963). Phys. Rev. Lett. 11, 237–238.
4. Kerr, R. P., and Schild A. (1969). Proc. Symp. Appl. Math. 17, 199; Debney, G. C., Kerr, R. P., and Schild A. (1969), J. Math. Phys. 10, 1842–1854; Urbantke, H. (1972), Acta. Phys. Austr. 35, 396; Debney, G. C. (1973), N. Cim. Lett. 8, 337.
5. Vaidya, P. C. (1972). Tensor N.S. 24, 315–321; Debney, G. C. (1974), J. Math. Phys. 15, 992–997; Bhatt, P. V., and Vaidya, S. K. (1991), Class. Quantum Grav. 8, 1717–1722.