using two chinese strains oftetrahymena pyriformis , s1 and bj4 , as the biological models , the effects of lighter rare earths ( lanthanum , cerium , praseodymium , neodymium , samarium , and europium ) , representatives of heavier rare earths ( yttrium and thulium ) , and mixed rare earths were studied .
C0043432
yttrium
C0025556
rare earths