theorem Th26:
  ==>.-relation(TS) reduces [x, u^w], [y, v^w] implies
  ==>.-relation(TS) reduces [x, u], [y, v]
proof
  assume ==>.-relation(TS) reduces [x, u^w], [y, v^w];
  then
  ex p being RedSequence of ==>.-relation(TS) st p.1 = [x, u ^w] & p.len p
  = [y, v^w] by REWRITE1:def 3;
  then
  ex q being RedSequence of ==>.-relation(TS) st q.1 = [x, u ] & q.len q =
  [y, v] by Th25;
  hence thesis by REWRITE1:def 3;
end;
