(;
GM[1]
SZ[19]
AW[gd][nc][mf][lp][mp][nq][mr][or][pq][qq][qn]
AB[pj][dj][dp][pd][pp][dd][df][pf][qp][op][np][oq][no][mo][lo][jp]
TR[mf]
C[Problem 55. Black to play.  

White has just played the marked stone with the dual intention of building a moyo at the top and reducing the scale of Black's moyo on the right. How should Black respond ? ]
(;B[qj]
TE[2]
C[Correct Answer.  

Black should reinforce his territory on the right with an 'iron pillar' at 1. ]
;W[gf]
C[If White jumps to 2, Black need not worry about White's moyo at the top. ]
(;B[pb]
LB[lc:A]
C[Black can simply defend the corner with 3 and aim to invade the top at A. <= ]
)
(;B[mh]
LB[pb:@]
C[Variation.  

Black 3 is an even stronger move than @. ]
;W[qc]
C[If White invades the corner with 4, ... ]
;B[pc];W[pb];B[qd];W[rb];B[rc]
C[... Black plays the sequence to 9, ending in sente. ]
;W[qb];B[kh]
C[He then jumps to 11 and builds a vast moyo in the center. <= ]
))
(;B[gf]
C[How the game continued.  

Capping with 1 was a good move, too, but ... ]
;W[ph]
C[... it let White start operations on the right with 2. ]
;B[qj]
C[Again, the 'iron pillar' of Black 3 is the key move. ]
;W[nh]
C[If White 4, ... ]
;B[qh]
C[... Black links up with 5. <= ]
)
)