private void backTrace(String word, String start, List<String> list) {
		if (word.equals(start)) {
			list.add(0, start);
			results.add(new ArrayList<String>(list));
			list.remove(0);
			return;
		}
		list.add(0, word);
		if (map.get(word) != null)
			for (String s : map.get(word))
				backTrace(s, start, list);
		list.remove(0);
	}