Explanatory notes
… if enriched in their radioactive isotopes (K 40, Rb 87, Sm 147, Lu 176, respectively), are to be considered as … (IV) below, and certain isotopes of thallium, lead, bismuth, polonium, radium, actinium or thorium, which are … which they were derived by radioactive conversion. Thus, bismuth 210 is called radium E , polonium 212 is called …