(;
AB[qq][pq][pp][po][qn][pl][ol][nm][no][nq]
AW[rq][qr][pr][or][nr][qp][qo][pn][pm][ql][qk][pk][ok][nk]
C[Black plays.

Source:
    "Tesuji", James Davies]
(;
B[qm]
C[A mistake.]
(;
W[rm]
C[The correct atari.];
B[ro]
(;
W[rp]
C[The only move.];
B[rn];W[sn]
C[White's stones hold together.]
)
    (;
    W[rn]
    C[A mistake.];
    B[rp];W[qn];B[rr]
    C[Ouch.]
    )
)
    (;
    W[rn]
    C[White returns the favor.];
    B[ro];W[rp];B[rm]
    C[Black gains a liberty to capture the 2 center stones.]
    )
)
    (;
    B[rn]
    C[Correct.  First, a forcing move.];
    W[ro];B[sn]
    C[Now Black springs the double threat move.]
    (;
    W[rp]
    C[The only way to save the lower right stones, but ...];
    B[qm]
    C[... Black changes direction to capture the 2 center stones.]
    )
        (;
        W[qm]
        C[White doesn't have time to save the 2 stones.];
        B[rp];W[sp];B[so]
        C[Black captures some stones.]
        )
        (;
        W[so]
        C[No better.];
        B[sp];W[rp];B[rr]
        C[Again, Black captures some stones.]
        )
    )
)

