(;
AB[br][cr][cq][dr][er][fq][gq][hq][iq][jq][jr][kq]
AW[ar][bq][bp][cp][do][dq][eq][fr][gr][hr][ir][jp]
C[White plays.

Source:  "Tesuji", Ch. 5, pp. 80-81]
(;
W[es]
C[Natural and wrong.

Both White and Black have four liberties,
so shouldn't White easily win the semeai
this way?];
B[fs]
C[Black unleashes a nasty surprise.];
W[gs];
B[ds];
W[bs]
C[And Black has a two step ko.
Yes, White has the advantage in the
ko, but White underestimated this
"simple" position.]
)
    (;
    W[fs]
    C[Correct.]
    (;
    B[is];
    W[es];
    B[hs];
    W[ds]
    LB[js:a]
    C[And White wins because Black still
has to make an outside move at A.]
    )
        (;
        B[as]
        C[Black can try to complicate things here.];
        W[bs];
        B[cs];
        W[es];
        B[as];
        W[aq];
        B[is];
        W[ds]
        C[But Black runs out of liberties.]
        )
    )
)
