(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[qm][rn][ro][np][op][pp][rp][jq][mq][qq][kr][lr][mr][pr][qr][ps]AB[om][no][oo][po][qo][lp][mp][qp][lq][nq][rq][rr][qs][rs]C[This is the problem position. Black to play]
(;B[oq]C[This is atari so could be correct]
(;W[or]C[However it gives white the chance to give up 3 stones...]
;B[nr]
;W[ns]
;B[pq]C[but this is not a connection and all get captured])
(;W[nr]C[This one is a connection though.]
;B[or]
;W[os]
;B[pq]
;W[ns]))
(;B[nr]
;W[ns]C[This fails as white can connect underneath.])
(;B[os]C[This way also fails]
(;W[or]C[This way white has to give up the three stones.]
;B[nr]
;W[ns]
;B[oq]
;W[ms]
;B[pq]
;W[os])
(;W[oq]C[This looks like it makes an eye]
(;B[nr]C[So black musn't play here])
(;B[or]C[This black captures four and rescues four.]
;W[nr]
;B[pq]))
(;W[nr]C[This way also allows black to rescue four and capture four.]
;B[or]))
(;B[pq]
;W[oq]C[The throw in clearly fails]
;B[nr]
;W[ns])
(;B[or]C[So this must be the tesuji.
Nothing white can do to save the four stones.]
(;W[pq]
;B[os])
(;W[oq]
;B[pq])
(;W[nr]C[This is the strongest white reply - He can save three
this way.]
;B[os]
;W[oq]
;B[pq])
(;W[os]
;B[ns]
;W[pq])
(;W[ns]
;B[os])))
