Vacuum polarization in light two-electron atoms and ions
  The original text has been changed substantially since the first version of this paper. Finally, we have decided to split that submission in two parts. Each of them includes a large number of updates and corrections. They were placed on ArXiv with new numbers (see: ArXiv:1110.3433 and 1111.2303). 
Alexei M. Frolov and David M. Wardlaw
nucl-th physics.atom-ph quant-ph