public ArrayList<String> find_baseNumOfCowork(){
		HashMap<String, String[]> coauthorSet = DataLoad.loadCoauthor();
		Collection<String> collection = coauthorSet.keySet();
		Iterator<String> iter = collection.iterator();
		while(iter.hasNext()){
			person = iter.next();
			temp = coauthorSet.get(person);
			if(temp.length >= 500){
				Master.add(person);
			}
		}
		return Master;
	}