Redshift constraints for RGB 0136+391 and PKS 0735+178 from deep optical imaging K. Nilsson, T. Pursimo, C. Villforth, E. Lindfors, L. O. Takalo and A. Sillanpää A&A, 547 (2012) A1 Published online: 19 October 2012 DOI: 10.1051/0004-6361/201219848