Table 4: The history of the 2-10 keV fluxes of 1H1219+301, H1426+428, Markarian 501 and PKS 0548-322 as observed by past X-ray missions.

Object	Mission	Date	a	Intrinsic absorption	Reference for flux value
1H1219+301	XMM-Newton	11/06/01	2.6	no	Table 3
	BeppoSAX	13/07/99	1.5	no	Costamante et al. (2001)
	ROSAT	18/06/92	2.7	no	Lamer et al. (1996)
	Einstein	05/06/79	1.1	yesb	Urry et al. (1986)
	Einstein	07/12/78	2.5	no	Urry et al. (1986)
H1426+428	XMM-Newton	16/06/01	2.9	no	Table 3
	BeppoSAX	08/02/99	2.0	no	Costamante et al. (2001)
	ASCA	06/02/94	1.6	yes	Sambruna et al. (1997)
	ROSAT	24/01/92	2.3	yes	Sambruna et al. (1997)
	BBXRT	09/12/90	3.5	yes	Sambruna et al. (1997)
Markarian 501	XMM	13/07/02	4.5	no	Table 3
	ASCA	26/03/96	6.6	no	Kubo et al. (1998)
	ROSAT	13/08/91	2.2	yes	Fink et al. (1991)
	ROSAT	25/02/91	1.3	no	Lamer et al. (1996)
	Einstein	22/08/79	2.7	yes	Ciliegi et al. (1993)
	Einstein	01/03/79	5.8	no	Ciliegi et al. (1993)
	Einstein	25/01/79	1.8	no	Ciliegi et al. (1993)
PKS 0548-322	XMM	03/10/01	2.5	no	Table 3
	BeppoSAX	07/04/99	1.5	no	Costamante et al. (2001)
	BeppoSAX	26/02/99	1.8	no	Costamante et al. (2001)
	BeppoSAX	20/02/99	2.3	no	Costamante et al. (2001)
	ASCA	30/10/93	2.8	yes	Sambruna & Mushotzky (1998)
	ROSAT	06/03/92	3.8	yesc	Lamer et al. (1996)
	Einstein	06/04/79	4.0	yes	Sambruna & Mushotzky (1998)
	Einstein	10/03/79	4.5	no	Ciliegi et al. (1993)

a 2-10 keV flux in 10 erg cm s. b Madejski et al. (1991). c Sambruna & Mushotzky (1998).