1. Examination of basic scientific principles for adding bio-gas to the natural gas grid;Burmeister,2009
2. Feasibility Study – Biogas upgrading and grid injection in the Fraser Valley;Electrigaz,2008
3. German Energy Agency (http://www.biogaspartner.de).
4. International Energy Agency (IEA) Bioenergy Task 37, Energy from Biogas. (http://www.iea-biogas.net).
5. UK Department of Energy and Climate Change (DECC) Biomethane into the gas network: a guide for producers, December 2009 (http://www.decc.gov.uk/assets/decc/what%20we%20do/uk%20energy%20supply/energy%20markets/gas_markets/nonconventional/1_20091229125543_e_@@_biomethaneguidance.pdf).