public boolean isLinked(Node node1, Node node2) {
		// on parcourt la liste des liens:
		for (Link link : this.links) {
			if ( (node1 == link.getStartNode() && node2 == link.getEndNode()) ||
				 (node2 == link.getStartNode() && node1 == link.getEndNode()) )
				return true;
		}
		return false;
	}