1. Ensemble spectral variability study of Active Galactic Nuclei from the XMM-Newton serendipitous source catalogue. (February 2016) Authors: Serafinelli, R; Vagnetti, F; Middei, R Journal: Journal of physics Issue: Volume 689(2016) Page Start: Record Type: Journal Article View Content: Available online (eLD content is only available in our Reading Rooms) ↗