If the stones at have two liberties left and it's white's move, then at is possible.
LukeNine45: This is the move my opponant made. After at a(my response), I can find no way to win the race for white.
LukeNine45: Actually, after looking at this again, your move with the net does appear to work.
The move at seems necessary. It threatens at and gives the tempo to connect at (above diagram) to capture the four black stones.
LukeNine45: I think this is the best white can do after (if both players forget about the net):