public static void writeAllSentences(List<List<String>> sentences,
			String outputFilePath) throws IOException {
		File output = new File(outputFilePath);
		if (!output.exists()) {
			output.createNewFile();
		}
		BufferedWriter bw = new BufferedWriter(new FileWriter(output));
		StringBuilder builder = new StringBuilder();
		for (List<String> group : sentences) {
			for (String sentence : group) {
				builder.append(sentence);
				builder.append("\n");
			}
			builder.append("\n");
		}
		bw.write(builder.toString());
		bw.close();
	}