改进题：In addition to visible trade, which involves the importing and exporting of tangible goods,there is also invisible trade, which involves the exchange of services between nations.

译文：除了这种进出口商品的有形贸易以外，还有一种国与国之间进行交换服务的无形贸易。

改进题：In addition to visible trade, which involves the importing and exporting of tangible goods,there is also invisible trade, which involves the exchange of services between nations.

译文：除了这种进出口商品的有形贸易以外，还有一种国与国之间进行交换服务的无形贸易。

改进的译文：除了这种进出口商品的有形贸易以外，还有一种国与国之间进行交换服务的无形贸易。