The HARPS search for southern extra-solar planets - XV. Six long-period giant planets around BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377, and HD 153950
C. Moutou, M. Mayor, G. Lo Curto, S. Udry, F. Bouchy, W. Benz, C. Lovis, D. Naef, F. Pepe, D. Queloz and N. C. Santos