1. Linde engineering: natural gas processing plants.
http://www.linde-engineering.com/internet.global.lindeengineering.global/en/images/HE_1_1_e_12_150dpi19_4271.pdf
. Accessed 31 Aug 2014
2. Shell global solution: sulfinol-X.
http://www.shell.com/business-customers/global-solutions/gas-processing-licensing/gas-processing-technolgies-portfolio/_jcr_content/par/textimage.stream/1469805944324/b7412e8c1d28341a55dc73852445a5e7ff45ab36d75b75ce3896c464e29d6048/factsheet-sulfinol-x.PDF
. Accessed 31 Aug 2014
3. Processing natural gas.
http://naturalgas.org/naturalgas/processing-ng/
. Accessed 24 Nov 2016
4. Gonzalez MR (2017) Transitioning refineries from sweet to extra heavy oil. In: Hsu CS, Robinson PR (eds) Springer handbook of petroleum technology. Springer, New York (Chapter 31)
5. Wikipedia: four-stroke engine.
https://en.wikipedia.org/wiki/Four-stroke_engine
. Access 31 Aug 2014