(;
AB[cq][dq][fq][gq][jq][lq][bp][cp][kp][pp][bn][gn][in][kn][bm][em][fm][gm][bl][ck][dk][fk]
AW[dp][ep][fp][gp][hp][ip][jp][co][cn][en][fn][qn][cm][cl][bk][qk][bj][cj]
PL[W]
C[White plays.

Source:
    Tesuji Dictionary, by Segoe Kensaku & Go Seigen];
W[bo]
C[Easy.  So far.

Note that White already has an eye in the center.];
B[ao];W[eq]
C[Also easy.  So far.];
B[er];W[dr]
(;
B[fr];W[an]
C[Another forcing move.];
B[am];W[cr];B[br];W[ar]
C[Fantastic move.  And the only move.  Incredibly, Black cannot avoid a liberty shortage along the left side!]
(;
B[ds]
C[The most obvious defense, but ...];
W[ap]
C[Another nice throw-in.]
(;
B[aq];W[ak];B[ap];W[al]
C[White catches the stones in a liberty shortage!]
)
    (;
    B[cs]
    C[Black cannot capture the stones fast enough.];
    W[ak];B[aq];W[al]
    )
)
    (;
    B[bq]
    C[No better.];
    W[ak];B[ap];W[al];B[an];W[bs]
    )
)
    (;
    B[cr]
    C[Blocking on the other side is no better.];
    W[fr]
    (;
    B[ds];W[gr]
    C[White captures 2 stones for the 2nd eye.]
    )
        (;
        B[gr];W[es];B[iq]
        C[Black can save the 3 stones to the left, but ...];
        W[ap];B[aq];W[an];B[am];W[ak];B[ap];W[al];B[an];W[br]
        C[... Black loses the semeai.]
        )
    )
)

