(;GM[1]FF[4]SZ[19]
GN[If Black gets the kosumi, defending at W1 is correct, ''a'' isn't sente anymore.]
PC[http://senseis.xmp.net/?EndgameTesuji12]AP[GoWiki:2009]
DT[2010-03-04]
C[Diagram from http://senseis.xmp.net/?EndgameTesuji12

If Black gets the kosumi, defending at W1 is correct, ''a'' isn't sente anymore.]
PL[W]

AB[eb][fc][fe]
AW[db][dd][cf]
LB[da:a]

;W[cc]C[W1]MN[1]

;LB[da:a]
)
