RussianTrick[exp, k, {q1,q2,p}] (=RussianTrick[exp,p,p,{q1,q2,p}]) does the integration by parts where p is the external momentum. RussianTrick[exp, k,l, {q1,q2,p}] (=RussianTrick[exp,k,l]) does integration by parts where l is the momentum to be differentiated.
The result is an expression which is vanishing.
See also: FourDivergence, FourLaplacian.
![[Graphics:Images/index_gr_1.gif]](Images/index_gr_1.gif)
![[Graphics:Images/index_gr_3.gif]](Images/index_gr_3.gif)
![[Graphics:Images/index_gr_5.gif]](Images/index_gr_5.gif)
![[Graphics:Images/index_gr_7.gif]](Images/index_gr_7.gif)
![[Graphics:Images/index_gr_9.gif]](Images/index_gr_9.gif)
![[Graphics:Images/index_gr_11.gif]](Images/index_gr_11.gif)
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