“…The zipper extends up to infinity. y = 2/3, so the Green function reads [2] G cl (x 1 ,y 1 ;α 1 ),(x 2 ,y 2 ;A) = G (x 1 ,y 1 ;α 1 ),(x 2 ,y 2 ;A) + G (x 1 ,y 1 ;α 1 ),(x 2 −y 2 ,1−y 2 ;B) , G cl (x 1 ,y 1 ;α 1 ),(x 2 ,y 2 ;B) = G (x 1 ,y 1 ;α 1 ),(x 2 ,y 2 ;B) + G (x 1 ,y 1 ;α 1 ),(x 2 −y 2 +1,1−y 2 ;A) .…”