(;
GM[1]
SZ[19]
AW[nc][nd][mf][lf][cf][dj][cn][qn][rp]
AB[dd][fd][jd][pd][oc][pf][nf][mg][dp][fp][pp][nq]
C[Problem 37. Black to play.  

White's stones at the top are heavy. How should Black attack them ? ]
(;B[ld]
TE[2]
C[Correct Answer.  

Black 1, threatening to separate the white stones, is the vital point of this position. ]
(;W[ne]
C[If White plays 2, ... ]
;B[ng]
C[... Black will connect at 3. ]
;W[le]
C[White must defend against the cut with 4 and ... ]
;B[jf]
TR[ld]
C[... Black continues the attack with 4. The marked black stone is on the vital point, depriving White of eye shape. <= ]
)
(;W[me]
C[Variation.  

White could draw back to 2. ]
;B[ng]
LB[ql:C][qc:A][hd:B]
C[Again, Black connects at 3. White would like to play A or B, but if she does, her stones at the top could get into trouble. On the other hand, Black is free to attack the white stones in the lower right with a pincer at C. <= ]
))
(;B[ne]
C[Failure.  

Black 1 is not a good move. ]
;W[ld]
C[It provokes White to play on the vital point of 2. White's stones now have more stability. <= ]
)
(;B[lg]
C[Failure.  

Pushing along the top with 1 ... ]
;W[kf];B[kg]
C[... and 3. just makes White strong. ]
;W[jf]
LB[hd:A]
C[Black is now vulnerable at the point A. <= ]
)
)