(;GM[1]FF[4]SZ[19]AP[SmartGo:0.4.1.2]CA[UTF-8]
GN[167ax]
PB[Black to play]
RU[Japanese]ST[2]
AB[oo:po][np:ns][qp:qr][rp]
AW[qm][pn][qo:ro][pp:pq][sp][oq:or][rq:rr]
(;B[pr]
C[If black tries to fill a white liberty the acpturing race is lost.];W[qs]
;B[op];W[ps])
(;B[op];W[qs];B[pr];W[ps])
(;B[qs]
C[Often descending to the edge works.]
(;W[ps]
C[This is one possible reply.]
(;B[os];W[rs]
C[White creates a snap-back.];B[pr];W[ps])
(;B[rs];W[pr]))
(;W[rs];B[os];W[ps]
C[This is another snap-back.]))
(;B[ps]
C[The diagonal move is the correct move.]
(;W[os]
C[White cannot interpose as it loses a liberty.];B[op])
(;W[pr]
C[The atari does not work either.];B[qs]
C[To interpose is self-atari and filling the other black liberty allows the black stones to escape.]
(;W[rs];B[os])
(;W[os];B[op]))
(;W[rs]
C[Black just escapes,];B[os];W[qs];B[pr])))

