Table 1: The astronomical databases used to build the reference catalogue. Database acronyms, objects class and the references for each catalogue are shown from left to right. GC and GP are the Galactic Center and Plane.

Database name	Objects class	References
XRB	X-ray binary systems	van Paradijs (1995)
HMXRB	High mass X-ray binary systems	Liu et al. (2000)
LMXRB	Low mass X-ray binary systems	Liu et al. (2001)
INTEGRAL-IBIS GP soft -ray catalogue	X-ray binary systems	Bird et al. (2004)
INTEGRAL-IBIS hard X-ray GC survey		Revnivtsev et al. (2004)
Swift-BAT high galactic latitude survey	AGN	Markwardt et al. (2005)
ZCAT	galaxies with B magnitude <14	Huchra et al. (1992)
AGN	Active galactic nuclei	Padovani et al. (1997) and
		private communication
RASS-BSC	ROSAT all-sky survey bright sources	Voges et al. (1999)
	with 0.1-2.4 keV flux > 10-11  erg s-1  cm-2
Sedentary	high energy peaked BL LACs (HBL)	Giommi et al. (1999), Giommi et al. (2005)
CABSCAT	Spectroscopic binary systems	Strassmeier et al. (1988), Strassmeier et al. (1993)
CVCAT	Cataclismic variable stars	Downes & Shara (1993)
ALLWARPS	Cluster of galaxies	Perlman et al. (2002)
BASSANI	Absorbed active galactic nuclei	private communication