Gokyo Shumyo, Section 1, Problem 90 / Attempts

First threaten, then tesuji  

The white group on itself does not live, so we have to try to make a move like sente on the right. It certainly threatens to live (if white plays at 2, she has two eyes, so the real problem comes after . Now looks like tesuji. Unfortunately, black has various ways to answer this. a to e all fail: if black plays a or b, white takes the other, similar with c and d. Black e is answered at a.

Most interesting (7 at the marked stone)  

The most interesting answer is here. It seems like in the sequence to , black has managed to turn the position into a ko, but white has the move at to save the day. Black cannot connect.

I think that the order of and in the first diagram can be reversed, by the way.

- Andre Engels