Now, black has a choice between securing the left and the right. If he secures the right, go after the left, and likewise, if he secures the left, play on the right as follows:
unkx80: This sequence from to is my intended solution, because white will take the ko first.
letsrock: The solution might not work in all cases. If fills at and black wins the ko on the left he can also secure the left group with b.
Anonymous: In either case white needs to win the ko on the undefended side...