689.17/299.38	MAYBE
689.17/299.38	
689.17/299.38	Problem:
689.17/299.38	 strict:
689.17/299.38	  f(a(),x) -> f(x,f(b(),x))
689.17/299.38	 weak:
689.17/299.38	  f(f(x,y),z) -> f(x,f(y,z))
689.17/299.38	  f(x,f(y,z)) -> f(f(x,y),z)
689.17/299.38	
689.17/299.38	Proof:
689.17/299.38	 Open
689.17/299.38	EOF