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http://go.nature.com/28SuW29
2. Rockefeller, J. D. Opening Statement of Hon. John D. Rockefeller IV, U. S. Senator from West Virginia (US Government Publishing Office, 2013);
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4. Lyons, B. In The Bridge Vol. 42, 13–19 (National Academy of Engineering, 2014).
5. Exhibit 7 U.S. Exports of Goods by End-Use Category and Commodity (U.S. Census Bureau, 2015).