1. BBC 2013 North American firms quit shale gas fracking in Poland http://www.bbc.co.uk/news/business-22459629
2. Bloomberg 2011 Shell ends shale gas search in Sweden; invests in China fields http://www.bloomberg.com/news/2011-07-28/shell-ends-shale-gas-search-in-sweden-invests-in-china-fields.html
3. Bloomberg 2012 German lawmakers reject ban on shale gas fracking in parliament http://www.bloomberg.com/news/2012-12-13/german-lawmakers-reject-ban-on-shale-gas-fracking-in-parliament.html
4. Geological characteristics and resource potential of shale gas in China;Caineng;Petrol Explor Dev,2010
5. Chevron 2012 The Gorgon project fact sheet http://www.chevronaustralia.com/Libraries/Chevron_Documents/May_2012_Gorgon_Project_Fact_Sheet.pdf.sflb.ashx