GRB060403: Search for an optical transient [Observed: 4 April 2006]
No optical counterpart for this gamma ray burst, down to mag 17.2,
14.9 hours after the event.
GRB041211: Search for an optical transient [Observation: 11 Dec 2004]
10 hours after the burst, no optical counterpart
down to mag 17.8.
GRB 030913 
Analysis of images of GRB 030913, with a negative result.