void assignOLSWeights( double[][] A )
	{
	  	edge e;
	  	e = depthFirstTraverse(null);
	  	while (null != e) 
	  	{
	  		if ( e.head.leaf() || e.tail.leaf())
	  			e.OLSext(A);
	  		else
	  			e.OLSint(A);
	  		e = depthFirstTraverse(e);
	  	}
	}