@Override
	public Graph addLink(Summit<T> start, Summit<T> end) {
		// TODO Auto-generated method stub
		if ( ! isSummitExist(start) ) addSummit(start);
			if ( ! isSummitExist(end) ) addSummit(end);
		   		Link<T> Link = new Link<T>(start, end);
		links.add(Link);
		return this;
	}