(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[9]KM[0.00]
PB[Noir]AW[ag][bg][cg][dg][eg][eh][ei]AB[af][bf][cf][df][ef][ff][fg][fh][fi]
(;B[ch]
(;W[ah]
(;B[bh]
(;W[ci]
;B[bi]
;W[di]C[seki])
(;W[bi]
;B[ci]C[ko indirect]))
(;B[bi]
(;W[di]
(;B[bh]
;W[ci]C[seki])
(;B[ci]
;W[bh]C[seki]))
(;W[ci]
;B[di]C[dead]))
(;B[ci]
(;W[bh]
;B[bi]
;W[di]C[seki])
(;W[bi]
;B[bh]C[indirect ko])))
(;W[bi]C[for reference, the book sequence]
;B[bh]
(;W[ci]C[to prevent the indirect ko ]
;B[ah]
;W[di]C[seki])
(;W[ah]
;B[ci]))
(;W[bh]
;B[bi]
;W[di]
;B[ah]C[another indirect ko]))
(;B[bi]C[this other attack is inferior]
;W[ch]
(;B[ci]
;W[di]
;B[ah]C[seki, but sente for White])
(;B[ah]
(;W[ci]
;B[di]C[even worse : Black loses a point])
(;W[bh]
(;B[ci]C[indirect ko]
;W[ai])
(;B[di]C[this way too]))))
(;B[bh]C[this attack fails completely]
(;W[ch]
;B[ci]
;W[bi]
;B[ai]
;W[ah])
(;W[bi]C[but one must be careful]
;B[ch]C[back to the correct attack]
;W[ci]
;B[ah]
;W[di])))