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		| Paper: | 
		The REX survey as a Tool to Test the Beaming Model for BL Lacs | 
	 
	
		| Volume: | 
		159, BL Lac Phenomenon | 
	 
	
		| Page: | 
		507 | 
	 
	
		| Authors: | 
		Caccianiga, A.; della Ceca, R.; Gioia, I. M.; Maccacaro, T.; Wolter, A. | 
	 
	
	
		| Abstract: | 
		We present the preliminary properties of the BL Lacs discovered in the REX survey (Caccianiga et al. 1998). In particular, we discuss a few sources with optical spectral properties ``intermediate'' between those of BL Lacs and those of elliptical galaxies. These objects could harbour weak (in the optical band) sources of non-thermal continuum in their nuclei and, if confirmed, they could represent the faint tail of the BL Lac population. The existence of such ``weak'' BL Lacs is matter of discussion in recent literature (e.g. Marcha et al. 1996) and could lead to a revision of the defining criteria of a BL Lac and, consequently, of their cosmological and statistical properties. | 
	 
	
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