1. C. Itzykson, J.B. Zuber, Quantum Field Theory (McGraw-Hill, New York, 1980)
2. C.D. Roberts, A.G. Williams, Prog. Part. Nucl. Phys. 33, 477–575 (1994)
3. The BABAR Collaboration, B. Aubert, et al, Phys. Rev. D69, 011103 (2004)
4. F. Ambrosino et al., Phys. Lett. B 608, 199–205 (2005)
5. KLOE2 Collab. and F. Jegerlehner, Phys. lett. B 767, 485492 (2017)