The XMM-Newton serendipitous survey - X. The second source catalogue from overlapping XMM-Newton observations and its long-term variable content
I. Traulsen, A. D. Schwope, G. Lamer, J. Ballet, F. J. Carrera, M. T. Ceballos, M. Coriat, M. J. Freyberg, F. Koliopanos, J. Kurpas, L. Michel, C. Motch, M. J. Page, M. G. Watson and N. A. Webb
