FEYN CALC SYMBOL

# RussianTrick

(=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.