theorem
  ==>.-relation(TS) reduces [x, w], [y, v^w] implies v = <%>E
proof
  assume ==>.-relation(TS) reduces [x, w], [y, v^w];
  then len w >= len(v^w) by Th75;
  then len v + len w <= 0 + len w by AFINSQ_1:17;
  hence thesis by XREAL_1:6;
end;
