Optical periodicity analysis for radio selected BL Lacertae objects (RBLs) J. H. Fan, R. G. Lin, G. Z. Xie, L. Zhang, D. C. Mei, C. Y. Su and Z. M. Peng A&A, 381 1 (2002) 1-5 Published online: 15 January 2002 DOI: 10.1051/0004-6361:20011356