Footnote 5. EPA, Green chemistry: https://www.epa.gov/greenchemistry

Textbox in subsection titled ‘Green chemistry’: https://sustainabledevelopment.un.org/

Footnote 6. Further detailed information about this green chemistry approach to producing ibuprofen can be found at http://www.ch.ic.ac.uk/marshall/4I6/Ibuprofen2.pdf