TesujiFromGames3/Solution

White to play  

This whole board problem consists of two parts
deciding which area of the board to play
deciding upon a particular move in that area

The area of interest is the black group in the lower right side.

The game is Kato Masao (white) vs Nie Weiping (black) played in Tokyo on 14 March 1988. It is the final game of the third China-Japan Super Go Series. The game is commented in the second chapter of The World of Chinese Go by Guo Juan.

Nie Weiping maintains that Black 89 and 91 where mistakes. These moves allowed the above sequence to take place. Black 89 and 91 should have been played as follows:

Black 89 and 91, corrected  

After this, white a, black b, white c and black d follow. Black has an eye on the side of the board. In the game diagram the black group is lacking this.