http://www.nejm.org/doi/full/10.1056/NEJM199812243392618 http://www.nejm.org/doi/full/10.1056/NEJM199812243392618 http://www.nejm.org/doi/full/10.1056/NEJM199812243392618 http://www.nejm.org/doi/full/10.1056/NEJM199812243392618