1. A. Kittur, et al., "The Future of Crowd Work. In Proc. CSCW (2013), 1301- 18.
2. J. Howe "The rise of crowdsourcing. Wired Magazine, 14(6). Available at: http://www.wired.com/wired/archive/14.06/crowds_pr.html. (2006).
3. U. Huws et al., "Crowd working survey: size of the UK's 'Gig Economy' revealed for the first time. FEPS. Available at: http://www.feps-europe.eu/assets/a82bcd12-fb97-43a6-9346-24242695a183/crowd-working-surveypdf.pdf. (2016c).
4. U. Huws et al., Crowd working survey: new estimate of the size of Dutch 'Gig Economy'. FEPS. Available at: http://www.feps-europe.eu/assets/778d57d9-4e48-45f0- b8f8-189da359dc2b/crowd-working-survey-netherlands-finalpdf.pdf. (2016a).
5. U. Huws et al., Crowd working survey: size of Sweden's 'Gig Economy' revealed for the first time. FEPS. Available at: http://www.feps-europe.eu/assets/3f853cec-1358-4fb4-9552-274b55e05ecf/crowd-working surveyswedenpdf.pdf. (2016b).