Triangular trade
It's hard to find examples that don't involve the trans-Atlantic slave trade.

http://johnquiggin.com/index.php/archives/2006/04/11/triangular-trade/
In some respects, the pattern of trade between Australia, China and the United States fits the triangular trade story neatly. Australia exports lots of raw materials to China, which in turn exports a wide range of manufactures to the US, which exports high-tech goods and services to Australia. Much the same story is true, with other Asian countries such as Japan in place of China.

http://papers.ssrn.com/sol3/papers.cfm?abstract_id=664524
We now study a triangular trade system of three countries (A, B, C) and three goods (fish c, wine w, and soybean s).
(It isn't specified if this example is based on any real-world situation.)

http://www.rieti.go.jp/en/events/bbl/05071901.html
A TTS has formed among these three regions. Japan/NIEs produce parts through high-technology, capital-intensive processes and export them to China and ASEAN. China and ASEAN, in turn, assemble such parts into final goods, capital goods or consumption goods, and export them to final markets such as the U.S. and EU, which consume such goods. Moreover, trade value in TTS has increased ((intermediate goods exports of Japan/NIEs to China/ASEAN) + (final goods exports of China/ASEAN to U.S./EU)). The share of TTS in total trade value has also more than doubled. Therefore, TTS has been strengthened.
(No mention is made of what the US exports to Japan.)