Explanatory notes
… of stable and radioactive isotopes, such as potassium, rubidium, samarium and lutetium ( heading 28.05 ), which, … heading. On the other hand, the same elements (potassium, rubidium, samarium, lutetium), if enriched in their … . To the natural radioactive isotopes potassium 40, rubidium 87, samarium 147, and lutetium 176 already …