public void mouseClicked(MouseEvent event) {
			GrammarTable gt = (GrammarTable) event.getSource();
			Point at = event.getPoint();
			int row = gt.rowAtPoint(at);
			if (row == -1)
				return;
			if (row == gt.getGrammarModel().getRowCount() - 1)
				return;
			Production p = gt.getGrammarModel().getProduction(row);
			Production[] pItems = Operations.getItems(p);
			JPopupMenu menu = new JPopupMenu();
			ItemMenuListener itemListener = new ItemMenuListener(p);
			for (int i = 0; i < pItems.length; i++) {
				JMenuItem item = new JMenuItem(pItems[i].toString());
				item.setActionCommand(pItems[i].getRHS());
				item.addActionListener(itemListener);
				menu.add(item);
			}
			menu.show(gt, at.x, at.y);
		}