public String toString() {
		StringBuffer sb = new StringBuffer(derivation);
		sb.append(", ");
		sb.append(Arrays.asList(productions) + ", ");
		sb.append('[');
		for (int j = 0; j < subs.length; j++) {
			if (j != 0)
				sb.append(", ");
			sb.append(subs[j]);
		}
		sb.append(']');
		return sb.toString();
	}