C. C. Sreejith, C. Muraleedharan, and P. Arun, “Life cycle assessment of producer gas derived from coconut shell and its comparison with coal gas: an Indian perspective”, Int. J. Energy Environ. Eng., vol. 4, no. 1 (December 2013), Feb. 2013, doi: 10.1186/2251-6832-4-8.