(;
GM[1]
SZ[19]
AW[cd][bc][be][gc]
AB[dp][pd][pp][cc][dc][ed]
LB[cd:1][ed:2][gc:3][cc:4][bc:5][dc:6][be:7]
C[Problem 139. Black to play.  

The moves to White 7 are a joseki. What should Black do next ? ]
;B[fe]
TE[2]
C[Correct Answer.  

Black 1 is the vital point. ]
(;W[dg]
C[If White defends the left side with 2, ... ]
;B[hd]
C[... Black plays 3 ... ]
;W[ic];B[hc];W[hb];B[gd]
C[... to 7 to get a thick position. ]
(;W[fc]
C[If White 8, ... ]
;B[gb]
C[... Black will cut at 9. <= ]
)
(;W[gb]
C[If White 8 here, ... ]
;B[je]
LB[jc:A]
C[... Black will play the knight's move of 9, increasing his thickness in the center and threatening to attach at A next. <= ]
))
(;W[id]
C[Variation.  

If White defends the top with 2, ... ]
;B[cf]
C[... Black attacks the white stones on the left with 3. ]
;W[cg]
C[White settles her stones with the tesuji of 4, but, ... ]
;B[dg];W[bg];B[dh]
C[... up to 7, Black gets thickness, ... ]
;W[ci];B[kd]
C[... enabling him to attack White at the top with the pincer of 9. <= ]
)
)