Variable stars in the open cluster NGC 6791 and its surrounding field F. De Marchi, E. Poretti, M. Montalto, G. Piotto, S. Desidera, L. R. Bedin, R. Claudi, A. Arellano Ferro, H. Bruntt and P. B. Stetson A&A, 471 2 (2007) 515-526 Published online: 26 June 2007 DOI: 10.1051/0004-6361:20077386