1. US Geological Survey: ‘Iron and steel’, ‘2007 minerals yearbook’, Advanced release, US Department of Interior, USGS, Rolla, MO, USA,April 2009, 37.5.
2. Midrex Technology Inc: ‘2008 world direct reduction statistics’, http://www.midrex.com/uploads/documents/MIDREXStatsBook2008.pdf (accessed October 2010)