Multi-band optical micro-variability observations of the BL Lac object S4 0954+658 I. E. Papadakis, V. Samaritakis, P. Boumis and J. Papamastorakis A&A, 426 2 (2004) 437-443 Published online: 11 October 2004 DOI: 10.1051/0004-6361:20040446