The broad band spectrum and variability of NGC 4151 observed by BeppoSAX A. De Rosa, L. Piro, G. C. Perola, M. Capalbi, M. Cappi, P. Grandi, L. Maraschi and P. O. Petrucci A&A, 463 3 (2007) 903-912 Published online: 19 December 2006 DOI: 10.1051/0004-6361:20065028