“…The equivalence of the 4pb(PC)-g coincidence counting system with the other international laboratories has been already established by participating in the international reference system (SIR) of Bureau International Des Poids Et Mesures (BIPM). The description of the system can be found elsewhere (Anuradha et al, 2005). The efficiency extrapolation technique (Campion, 1959;Baerg, 1966) was used for the standardization.…”