Optical observations of eight X-ray selected BL Lacertae objects C. M. Raiteri, M. Villata, G. De Francesco, L. Lanteri, M. Cavallone and G. Sobrito Astron. Astrophys. Suppl. Ser., 132 3 (1998) 361-365 Published online: 15 November 1998 DOI: 10.1051/aas:1998300