theorem Th8:
  the_sort_of (o-term p) = the_result_sort_of o
  proof
    reconsider t = o-term p as Term of S,X by MSAFREE4:42;
    [o,the carrier of S] = t.{} by TREES_4:def 4;
    then the_sort_of t = the_result_sort_of o by MSATERM:17;
    hence thesis by Th5;
  end;
