Equation Icon  ab c′d′ N [G ] = g g N[a(bc′d′[G] ) ( ) ] 2 1- p′ 2 1- ′ p = − 3 G ξ m + 2 ξR G;p′ + m + 2ξR G;p 2( ) ( ) ( ) + 9ξ-- G ′p′ G p + G G p ′p′ + m2 + 1ξR m2 + 1-ξR ′ G2 2 ;p ;p ;p p 2 2 ( 1 ) [ ( 1 ) ′ ( ′ ′) +3 --− ξ 3 --− ξ G;p′pG;p p − 3ξ G;p G;p′pp + G;p′ G;ppp 6 ( 6 ) ( ) ] 2 1 p′ 2 1 ′ ;p + m + -ξR G;p′ G; + m + --ξR G;p G . (80 ) 2 2