Long-term radio variability of AGN: flare characteristics T. Hovatta, E. Nieppola, M. Tornikoski, E. Valtaoja, M. F. Aller and H. D. Aller A&A, 485 1 (2008) 51-61 Published online: 06 May 2008 DOI: 10.1051/0004-6361:200809806