Explanatory notes
… praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium). The heading also covers compounds … metal compounds . Yttrium oxide (yttria), terbium oxide (terbia), mixtures of ytterbium oxides (ytterbia) and of …