Low-energy pions in nuclear matter and ππ photoproduction within a BUU transport modelO. Buss, L. Alvarez-Ruso, P. Mühlich and U. MoselEur. Phys. J. A, 29 2 (2006) 189-207DOI: https://doi.org/10.1140/epja/i2006-10075-y