reserve T for BinContinuous unital TopSpace-like non empty TopGrStr,
  x,y for Point of I[01],
  s,t for unital Point of T,
  f,g for Loop of t,
  c for constant Loop of t;
reserve
  T for TopologicalGroup,
  t for unital Point of T,
  f,g for Loop of t;

theorem Th13:
  LoopMlt(f,g),LoopMlt(g,f) are_homotopic
  proof
    take HopfHomotopy(f,g);
    thus thesis by Lm3;
  end;
