All approaches to RKKY interaction in graphene are equal, but some   approaches are more equal than others
  We show explicitly that two approaches to calculations of RKKY interaction between two magnetic impurities in graphene based on Green's functions: one using coordinate--imaginary time representation, and the other using momentum--frequency representation, give exactly the same results and none of them has to operate with diverging integrals and implement the cut-off procedure. Together with this, we claim that the first approach is more convenient for the calculations than the second one. 
E. Kogan
cond-mat.mes-hall cond-mat.stat-mech