public List<Tuple<BigInteger, BigInteger>> getPosSentences() {

		List<Tuple<BigInteger, BigInteger>> result = new ArrayList<Tuple<BigInteger, BigInteger>>();
		ListIterator<Tuple<BigInteger, BigInteger>> goalIter = goals
				.listIterator();
		Tuple<BigInteger, BigInteger> currTuple = null;
		while (goalIter.hasNext()) {
			
			currTuple = goalIter.next();
			Tuple<Annotation,Boolean> sentence = findSentence(currTuple);

			if (sentence != null) {
				Tuple<BigInteger, BigInteger> sentenceTuple = new Tuple<BigInteger, BigInteger>(
						sentence.x.getStartNode(), sentence.x.getEndNode());
				result.add(sentenceTuple);
			}
		}
		return result;
	}