1. P A M Dirac,Proc. R. Soc. London A167, 148 (1938)
2. F Rohrlich,Classical charged particles (Addison-Wesley, Reading, Mass. 1965)
3. J L Jiménez,Ciencia 40, 257 (1989)
4. H B Bhabha,Proc. R. Soc. London A172, 381 (1939)
5. J L Synge,Ann. Mat. Pura Appl. 83, 33 (1970)