(;
GM[1]
SZ[19]
AW[kc][od][pc][qc]
AB[dc][ce][ic][rc][qd][re][pf]
TR[pf][ic]
C[Problem 37. Black to play.  

Since Black has played the two marked stones, he dominates the top of the board. From this strength, where should he invade ? ]
;B[mc]
TE[2]
C[Correct Answer.  

Jumping into the middle of White's formation with 1 is the vital point. ]
;W[md]
C[If White attaches with 2, ... ]
;B[lc];W[ld];B[kb]
(;W[kd];B[jc]
C[... Black links up his stones with the moves to 7. <= ]
)
(;W[nc]
C[Variation.  

If White settles herself with 6, ... ]
;B[kd];W[ke];B[jd]
LB[kd:7]
C[... Black is more than happy to play 7 and 9. <= ]
)
)