B1422+231: The influence of mass substructure on strong lensing M. Bradač, P. Schneider, M. Steinmetz, M. Lombardi, L. J. King and R. Porcas A&A, 388 2 (2002) 373-382 Published online: 31 May 2002 DOI: 10.1051/0004-6361:20020559