
https://www.parliament.uk/documents/commons-committees/culture-media-and-sport/Background%20paper%20-%202016%20Referendum%20Expenses%20Opinion%20-%20Matrix%20Chambers.pdf

http://www.cesifo-group.de/ifoHome/publications/working-papers/CESifoWP/CESifoWPdetails?wp_num=6438&CESifoWP.search=+

https://www.lobbying.ie/media/6072/regulation-of-lobbying-annual-report-2016-final-web.pdf