Deep optical imaging of radio selected BL Lacertae objects T. Pursimo, K. Nilsson, L. O. Takalo, A. Sillanpää, J. Heidt and H. Pietilä A&A, 381 3 (2002) 810-824 Published online: 15 January 2002 DOI: 10.1051/0004-6361:20011564