1. The Extreme Light Infrastructure (ELI) project: http://www.extreme-light-infrastructure.eu/elihome.php
2. W. Heisenberg, H. Euler, Z. Phys. 98, 714 (1936); english translation at e-print arXiv:physics/0605038
3. G.V. Dunne, Ian Kogan Memorial Collection, From Fields to Strings: Circumnavigating Theoretical Physics, edited by M. Shifman et al., Vol. 1, pp. 445–522 [arXiv:hep-th/0406216]
4. V. Weisskopf, Kong. Dans. Vid. Selsk. Math-fys. Medd. XIV No. 6 (1936);
5. English translation in: Early Quantum Electrodynamics: A Source Book, edited by A.I. Miller (Cambridge University Press, 1994)