(;GM[1]FF[4]SZ[19]
GN[Double snapback]
PC[http://senseis.xmp.net/?SnapbackProblem21/Solution]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?SnapbackProblem21/Solution

Double snapback]
PL[B]

AB[ea][ab][bb][eb][cc][ec][cd][dd][ed]
AW[fa][cb][fb][ac][bc][fc][bd][fd][be][ce][de][ee][fe]
CR[cb]

;B[ca]C[B1]MN[1]
;W[db]C[W2]MN[2]
;B[da]C[B3]MN[3]
;W[ba]C[W4]MN[4]

;CR[cb]
)
