Statistical analyses of long-term variability of AGN at high radio frequencies T. Hovatta, M. Tornikoski, M. Lainela, H. J. Lehto, E. Valtaoja, I. Torniainen, M. F. Aller and H. D. Aller A&A, 469 3 (2007) 899-912 Published online: 02 May 2007 DOI: 10.1051/0004-6361:20077529