public List<Item> getItemsOnPosition(Position position) {
		if (!validPosition(position))
			throw new IllegalArgumentException("The given position isn't valid!");

		List<Item> posItems = new ArrayList<Item>();

		for (Element element : getElementsOnPosition(position)) {
			if (element instanceof Item)
				posItems.add((Item) element);
		}

		return Collections.unmodifiableList(posItems);
	}