(;
GM[1]
SZ[19]
AW[ce][ed][fd][gd][he][hf][if][jf][pp][qo][mq][oc][pc][mc]
AB[dc][ec][fc][hc][hd][ie][je][ke][kf][dp][fq][qj][qc][qd][pd][od]
TR[hc][hd][ie][je][ke][kf][mc][oc][pc]
C[Problem 61. Black to play.  

Black's marked stones are thick, so the marked white ones are in trouble. Where should Black start his attack ? ]
(;B[lb]
TE[2]
C[Correct Answer.  

Black 1 on the second line is the vital point because it threatens White's base. Moreover, because the black stones are thick, White cannot easily escape into the center. ]
(;W[nd]
C[If White bulges out with 2, ... ]
;B[ne]
C[... Black keeps the white stones confined with 3 ... ]
;W[me];B[mf]
C[... and 5. ]
;W[qb];B[rb];W[nf];B[oe];W[mb];B[le];W[kc];B[lc];W[ld]
C[The sequence continues to 14, but ... ]
;B[md]
C[... Black starts a ko with 15. White has no ko threats, so Black will capture all of White's stones. <= ]
)
(;W[lc]
C[Variation.  

If White 2 here, ... ]
;B[kb]
C[... Black will extend to 3. <= ]
))
(;B[kc]
C[Failure.  

Black 1 is slack. ]
;W[qb]
C[After exchanging 2 ... ]
;B[rb]
C[... for 3, ... ]
;W[nd]
LB[nf:B][lb:A]
C[... White plays 4. A and B are now miai.  

 

 

- if Black A, White escapes with B; if Black B, White makes two eyes with A. <= ]
(;B[lb]
C[If Black 5 here, ... ]
;W[nf]
C[... White escapes with 6. <= ]
)
(;B[nd]
C[Failure.  

Black 1 is a vital point, but, ... ]
;W[qb]
C[... after exchanging 2 ... ]
;B[rb]
C[... for 3, ... ]
;W[lb]
C[... White plays 4 and gets two eyes. ]
(;B[jb]
C[That is, if Black 5 here, ... ]
;W[qa]
C[... White defends at 6. ]
)
(;B[pb]
TR[qb]
C[If Black capture the marked stone with 5, ... ]
;W[ob]
C[... White ataris once, ... ]
;B[qa];W[jb]
C[... then jumps to 8. <= ]
))
(;B[nf]
C[If Black 5 here, ... ]
;W[lb]
C[... White makes two eyes with 6. <= ]
))
)