* @return result  a LinkedHashSet of the people found in sentences
     */
    private static LinkedHashSet<String> people(
            ArrayList<ArrayList<String>> sentences) {
        LinkedHashSet<String> result = new LinkedHashSet<String>();
        for (int i = 0; i < sentences.size(); i += 1) {
            String type = sentences.get(i).get(1);
            if (type.equals(ASSERTION_TYPES.get(0))
                    || type.equals(ASSERTION_TYPES.get(2))
                    || type.equals(ASSERTION_TYPES.get(4))
                    || type.equals(ASSERTION_TYPES.get(5))
                    || type.equals(ASSERTION_TYPES.get(6))
                    || type.equals(QUESTION_TYPES.get(0))
                    || type.equals(QUESTION_TYPES.get(5))
                    || type.equals(QUESTION_TYPES.get(7))) {
                result.add(sentences.get(i).get(2).toLowerCase());
            }
        }
        return result;
    }