1. B. Mashhoon, Phys. Lett. A 145 (1990) 147.
2. B. Mashhoon, Phys. Lett. A 143 (1990) 176.
3. A. M. Eisele, Helv. Phys. Acta 60 (1987) 1024.
4. B. Mashhoon: Black Holes: Theory and Observation, Lecture Notes in Physics 514, edited by F. W. Hehl, C. Kiefer and R. J. K. Metzler ( Springer, Heidelberg, 1998 ) pp. 269–284.
5. J. C. Maxwell, Nature 21 (1880) 314.