double complex function atreesl(j1,j2,j3,j4,j5,j6,za,zb) 
      implicit none
      include 'constants.f'
      include 'zprods_decl.f'
      include 'sprods_com.f'
      integer j1,j2,j3,j4,j5,j6
      double precision t
c-----Note all tree amplitudes divided by im wrt to BDK paper
      atreesl=-((za(j4,j5)*zb(j1,j3)
     . *(-(za(j1,j2)*zb(j1,j6))+za(j2,j3)*zb(j3,j6)))/
     . (s(j1,j2)*s(j5,j6)*t(j1,j2,j3))) 
     . +(za(j2,j4)*(za(j2,j5)*zb(j1,j2)+za(j4,j5)*zb(j1,j4))*zb(j3,j6))/
     . (s(j1,j2)*s(j5,j6)*t(j1,j2,j4))
      return
      end