The purchase of that literature has become hugely more expensive because, since it has to be bought through European firms with branches in the United States, air-freight costs raise the overall cost of the literature by 15 per cent.
购买文献变得十分昂贵，因为需要通过在美国设有分公司的欧洲公司购买，以文献的净值计，空运成本要高15％。