See "Exemplary documents: a foundation for information retrieval design," by David C. Blair and Steven O. Kimbrough, Information Processing and Management, vol. 38, no. 3, pages 363-379, 2002.

1. EU biofuel policy is a 'mistake', BBC, 2007-08-18.
2. Biofuels switch a mistake, say researchers, The Guardian, 2007-08-17.
3. Energy transitions past and future by Cutler Cleveland.
4. New Zeeland, "7 Implications of Higher Oil Prices for the Primary Sectors".
5. "Cooking Up More Uses for the Leftovers of Biofuel Production". As PDF.