Double Pion Production Reactions
  We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent two pion photoproduction in nuclei are also reported. 
E. Oset, J. A. Gomez Tejedor, F. Cano, J. C. Nacher, S. Kamalov, L.   Alvarez-Ruso and E. Hernandez