1. F. Sauter, Über das Verhalten eines Elektrons im homogenen elektrischen Feld nach der relativistischen Theorie Diracs, Z. Phys.69 (1931) 742 [INSPIRE].
2. W. Heisenberg and H. Euler, Consequences of Dirac’s theory of positrons, Z. Phys.98 (1936) 714 [physics/0605038] [INSPIRE].
3. V. Weisskopf, The electrodynamics of the vacuum based on the quantum theory of the electron, Kong. Dan. Vid. Sel. Mat. Fys. Med.14N6 (1936) 1.
4. J.S. Schwinger, On gauge invariance and vacuum polarization, Phys. Rev.82 (1951) 664 [INSPIRE].
5. G.V. Dunne, Heisenberg-euler effective lagrangians: Basics and extensions, in From Fields to Strings: Circumnavigating Theoretical Physics (2005), pp. 445–522, [DOI].