1. A.I. Akhiezer,
V.B. Beresteskii,
Quantum electrodynamics
(Nauka Science,
Moscow,
1981) in Russian; Interscience, New York, 1965
2. W. Greiner,
J. Reinhardt,
Quantum electrodynamics, 4th edn.
(Springer Verlag,
Berlin,
2010)
3. E.A. Uehling,
Phys. Rev. 48, 55
(1935)
4. E.H. Wichmann,
N.H. Kroll,
Phys. Rev. 101, 843
(1956)
5. P. Pyykkö,
M. Tokman,
L.N. Labzowsky,
Phys. Rev. A 57, R689
(1998)