1·Even the two rarest (thulium and lutetium) are more widely spread throughout the Earth's crust than gold or platinum.
即使是最稀有的那两个(铥和镏)在全球地壳中也比金或铂要多。
2·Lanthanide: Any of the series of 15 consecutive chemical elements in the periodic table from lanthanum to lutetium (atomic numbers 57-71).
镧系：周期表中从镧到镏（原子序数57～71）15种按顺序排列的化学元素系列。