Hadron-pair photoproduction in longitudinally polarized lepton–nucleon collisions C. Hendlmeier, M. Stratmann and A. Schäfer Eur. Phys. J. C, 48 1 (2006) 135-145 Published online: 28 September 2006 DOI: 10.1140/epjc/s10052-006-0013-9