We know how Wal-Mart has battered its competition in the United States, in large part by buying in enormous volume from China. The world's largest retailer is also the world's largest importer of Chinese goods. Now the Arkansas-based giant is looking to China as a source of customers. But it's a competitive market. The BBC's Stephen Evans goes deep inside a Chinese Wal-Mart as part of Think Global, public radio's week of special coverage.