Close pairs of quasars with different redshifts: New observations and resultsD. Sluse, J. Surdej, J.-F. Claeskens, Y. De Rop, D. W. Lee, A. Iovino and M. R. S. HawkinsA&A, 397 2 (2003) 539-544DOI: https://doi.org/10.1051/0004-6361:20021524