Hard X-ray spectral variability of the brightest Seyfert AGN in the Swift/BAT sample M. D. Caballero-Garcia, I. E. Papadakis, F. Nicastro and M. Ajello A&A, 537 (2012) A87 Published online: 12 January 2012 DOI: 10.1051/0004-6361/201117974