1. Albert. Einstein, Akademie-Vortrage 25, 88 (1915)
2. Richard C. Tolman, Phys. Rev. 55, 364 (1939)
3. L. Kayll, Phys. Rev. D 67, 104015 (2003)
4. D. Hans Stephani, Malcolm A.H. Kramer, Cornelius H. MacCallum, H. Eduard, Cambridge Monographs on Mathematical Physics (Cambridge University Press, Cambridge, 2003)
5. M.S.R. Delgaty, L. Kayll, Comput. Phys. Commun. 115, 395 (1998)