Ahrens, J Helicity dependence of gammap --> Npi below 450 MeV and contribution to the Gerasimov-Drell-Hearn sum rule. [electronic resource] - Physical review letters Jun 2000 - 5950-4 p. digital Publication Type: Journal Article ISSN: 0031-9007 Standard No.: 10.1103/PhysRevLett.84.5950 doi