1. Lukačević, I. (1986).Gen. Rel. Grav.,18, 923.
2. Rosen, N. (1976),Topics in Theoretical and Experimental Gravitation Physics (Plenum Press, New York), 273.
3. Rosen, N. (1979),Gen. Rel. Grav.,10, 639.
4. Synge, J. (1960).Relativity: The General Theory (North-Holland, Amsterdam) 318.