(;AB[os][qr][or][rq][qq][pq]AW[rs][nr][oq][lq][jq][hq][rp][op][mp][jp][qo][pn]C[White plays.

Source:
    Qi Jing Zhong Miao #151, an ancient collection of mostly kyu level life and death problems.

Analysis:
    Myron Souris]SZ[19]

(;W[qs];B[mr];W[nq];B[ns];W[ls]C[The only move that works.];B[lr];W[ps]
(;B[kr];W[ms];B[ks];W[ms];B[ls];W[sq]C[Note that all of White's stones on the left are necessary for White to hane here on the right!  Otherwise, Black could escape toward the lower left corner.];B[sr];W[sp]LB[pr:A][rr:B]C[Black is dead!
For example, White fills the outside liberties, Black has to fill at A, but then White captures at B anyway.])
(;B[sr]C[Black is 1 liberty short of a living shape in the corner.];W[pr];B[ms];W[kr]))
(;W[sq]C[Bad timing];B[sr];W[qs];B[sp]C[White's 1st play needlessly allows Black to cause mischief.]
(;W[so]C[If White blocks Black from escaping up the right side, ...];B[mr];W[nq];B[ns];W[ls];B[lr];W[ps];B[pr]C[Black has a ko and 3 internal ko threats.])
(;W[ns]C[If White keeps Black to 1 eye in the corner, ...];B[ro];W[qp];B[rn];W[qm];B[rl]C[And unless White has help up the right side, Black escapes.])))