(;
AB[rr][rs][qq][qp][pp][rn][rl][qk][rj][pk]
AW[qr][pr][pq][oq][op][po][pn][pl][ok][oj][pj][qi][ri][ro]
TR[ro]
C[Black's response to the marked play?

Source:
    "Tesuji", James Davies, chapter 7, section 3]
(;
B[qo]
C[The only line the book gives.];
W[qn];B[rp];W[rm];B[so];W[sm]
C[But Black takes a big 20 point loss by letting go of the 4 stones above.]
)
    (;
    B[rp]
    C[The book doesn't show this more interesting defense, which in a real game could easily be better for Black than the book line.]
    (;
    W[qn]
    (;
    B[so]
    C[Now Black can dodge to here.];
    W[rm];B[sm]
    C[For risking only about 4 more points, Black has this ko to save the 20 or so points that the top 4 Black stones represent.  Notice that White has no internal ko threats.]
    )
        (;
        B[rm]
        C[Too greedy];
        W[sp]
        C[Black dies in the corner (but lives in gote on the right side).];
        B[sk]
        )
    )
        (;
        W[rm]
        C[Fails.  Now Black lives with all his stones!]
        (;
        B[qn];W[qo];B[so];W[qm];B[sm]
        (;
        W[sq];B[sp]
        C[Black hangs onto the stones at the top, and if necessary, makes a 2nd eye on the middle right side.]
        (;
        W[sj];B[sk]
        )
            (;
            W[sk];B[sl]
            )
            (;
            W[sr];B[sj]
            )
        )
            (;
            W[sk];B[sl];W[sq];B[sp];W[sj];B[sr]
            )
            (;
            W[sj];B[sp]
            )
        )
            (;
            B[qm]
            C[A mistake];
            W[qn];B[sm];W[sp];B[so]
            C[Now White has the ko back.]
            )
        )
        (;
        W[qo]
        C[Too slow];
        B[so];W[sq];B[sp]
        C[If necessary, Black has a 2nd eye on the middle right side.]
        )
    )
)

