Discovery of four gravitational lensing systems by clusters in the SDSS   DR6
  We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 (SDSS DR6). Two of the four systems show Einstein rings while the others show tangential giant arcs. These arcs or rings have large angular separations (>8") from the bright central galaxies and show bluer color compared with the red cluster galaxies. In addition, we found 5 probable and 4 possible lenses by galaxy clusters. 
Zhong-Lue Wen, Jin-Lin Han, Xiang-Yang Xu, Yun-Ying Jiang, Zhi-Qing   Guo, Peng-Fei Wang, Feng-Shan Liu