ABSTRACT
If y 0 is in fr(/?) and is not x , then it is mapped to t 0 by 7/*. It follows from (A ), applied to 7 , 7 ', that x ’ is not in occ(t0) ; thus y 0 is mapped to t 0 by the first map in (16). On the other hand, y 0/ x im plies that y 0 remains fixed under C (x,s)1? and being so in fr(a) it then is mapped to t 0 by r )y .
