(;GM[1]FF[4]SZ[19]
GN[Ko threat]
PC[http://senseis.xmp.net/?UnderTheStonesProblem4/Solution]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?UnderTheStonesProblem4/Solution

Ko threat]
PL[B]

AB[dn][en][fn][gn][bo][do][ho][cp][aq][bq][gq][hq][cr][dr][hr][hs]
AW[eo][dp][fp][cq][dq][eq][fq][ar][br][er][gr][gs]

;B[cs]C[B1]MN[1]
;W[fs]C[W2]MN[2]
;B[fo]C[B3]MN[3]
;W[ds]C[W4]MN[4]
;B[es]C[B5]MN[5]
;W[bp]C[W6]MN[6]

;
)
