private Map<Integer,Site> sitesHasVar(int index) {
		Map<Integer,Site> sitesHasVar = new HashMap<Integer, Site> ();
		for (int i: sites.keySet()) {
			Site site = sites.get(i);
			if (site.hasVariable(index)) {
				sitesHasVar.put(i, site);
			}
		}
		return sitesHasVar;
	}