Generating functional for mesonic ChPT with virtual photons in a general covariant gauge Andria Agadjanov, Dimitri Agadjanov, Anzor Khelashvili and Akaki Rusetsky Eur. Phys. J. A, 49 9 (2013) 120 Published online: 23 September 2013 DOI: 10.1140/epja/i2013-13120-x