public ArrayList<Book> bookQuery(String query){
		ArrayList<Book> results = new ArrayList<>();
		for(int i = 0;i < repository.size();i++){
			if(repository.get(i).getIndex().hasTerm(query) || repository.get(i).getTOC().hasTerm(query)){
				results.add(repository.get(i));
			}
		}
		if(results.size() != 0){
			return results;
		}
		else {
			return null;
		}
	}