The variable X-ray spectrum of Markarian 766 - I. Principal components analysis L. Miller, T. J. Turner, J. N. Reeves, I. M. George, S. B. Kraemer and B. Wingert A&A, 463 1 (2007) 131-143 Published online: 20 November 2006 DOI: 10.1051/0004-6361:20066548