On the Lx – L6 μm ratio as a diagnostic for Compton-thick AGN I. Georgantopoulos, E. Rovilos, A. Akylas, A. Comastri, P. Ranalli, C. Vignali, I. Balestra, R. Gilli and N. Cappelluti A&A, 534 (2011) A23 Published online: 23 September 2011 DOI: 10.1051/0004-6361/201117400