Mao, Andrew, Ece Kamar, Yiling Chen, Eric Horvitz, Megan Schwamb, Chris Lintott, and Arfon Smith. 2013. “Volunteering Versus Work for Pay: Incentives and Tradeoffs in Crowdsourcing”. Proceedings of the AAAI Conference on Human Computation and Crowdsourcing 1 (1):94-102. https://doi.org/10.1609/hcomp.v1i1.13075.