(;
GM[1]
SZ[19]
AW[cd][ed][jc][mc][qf][pf][qj][oj]
AB[oc][pd][qe][cj]
C[Problem 129. White to play.  

The shape of the black stones is called 'the three crows'. This is a very solid formation, but is still vulnerable to an invasion if White has built up strong positions in the vicinity. Where does White invade ? ]
;W[qc]
TE[2]
C[Correct Answer.  

White 1 is the vital point. ]
(;B[qd]
C[Black 2 is the severest response. ]
;W[pb];B[ob];W[rb];B[rd];W[qa];B[rc];W[pc];B[sb]
C[After 10, ... ]
;W[od]
LB[ra:A]
C[... White cuts at 11, and the life or death of the stones in the corner depends on a ko starting at A. <= ]
)
(;B[rd]
C[Variation.  

If Black 2 here, ... ]
;W[rc];B[rf];W[ob];B[nb];W[pb];B[nc];W[mb];B[na];W[rb]
C[... White easily lives with the moves to 11. <= ]
)
)