private void tracing(int position) {
		Person pNow, pNext;
		int direction, i, label;

		label = path[position].getLabel();
		direction = Integer.signum(label);
		label -= direction;
		while (label != 0) {
			pNow = path[position];
			Person ca[] = pNow.getCoauthors();
			for (i = 0; i < ca.length; i++) {
				pNext = ca[i];
				if (!pNext.hasLabel())
					continue;
				if (pNext.getLabel() == label) {
					position -= direction;
					label -= direction;
					path[position] = pNext;
					break;
				}
			}
		}
	}