Neutral pion photoproduction at high energies A. Sibirtsev, J. Haidenbauer, S. Krewald, U. -G. Meißner and A. W. Thomas Eur. Phys. J. A, 41 1 (2009) 71-84 Published online: 06 May 2009 DOI: 10.1140/epja/i2009-10771-0