(;
GM[1]
SZ[19]
AW[dg][ek][cn][dn][ho][hp][hr][jo][ko][mp][ej][qh][ip]
AB[jp][jd][pj][dj][dp][pd][pp][dd][gc][co][fp][go][gn][jn][qm][hn][cd][io][in][fr]
LB[cd:1][qh:2]
TR[ej]
C[Problem 30. Black to play.  

After White played the marked stone in Problem 26, Black took the corner territory in the upper left with 1. White switched to the right side with 2. How can Black take a decisive lead ? ]
(;B[qf]
TE[2]
C[Correct Answer.  

The checking-extension of Black 1 is severe because it robs White of a base to settle her stone. ]
;W[oh];B[oq]
LB[oc:B][mh:A]
C[Next, Black reinforces his lower right corner while threatening to reduce White's territory at the bottom. Since White's two stones in the upper right are weak, she must strengthen them by jumping to A before she can consider invading the top. But Black will then reinforce his position in the upper right corner with B. <= ]
)
(;B[qj]
C[How the game continued.  

Black 1 was not appropriate in this position. It enabled White ... ]
;W[qd];B[qc];W[qe];B[pc];W[of]
C[... to make a base for her stones with the sequence to 6. With three stable positions, White could now think about fighting for territory with an invasion at the top or the 3-3 point in the lower right corner. <= ]
)
)