“…Considering the fact that ei"''=V .da(P,Pa, P2) 1 = vs(sin f}_a, 2 _)-1 (cos~J-1 , at .ds (P, Pa, P2) = 0. A similar procedure can be made at .d3 C!,.Pa, Pi) =0 (i=3, 4) and finally we get the helicity amplitude by combining the result of 3A):(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) This is free from kinematical singularities at .d8 (P, Pa, Pi) =. 0 (i = 1, 2, 3, 4).…”