theorem Th73:
  x, v -->. y, TS implies ==>.-relation(TS) reduces [x, v^w], [y, w]
proof
  assume x, v -->. y, TS;
  then <*[x, v^w], [y, w]*> is RedSequence of ==>.-relation(TS) by Th58;
  then [[x, v^w], [y, w]] in ==>.-relation(TS) by Th8;
  hence thesis by REWRITE1:15;
end;
