Ahmad, Syedah, Robert Lensink, and Annika Mueller. “Boosting Survey Response Rates by Announcing Undefined Lottery Prizes in Invitation Email Subject Lines Evidence from a Global Randomized Controlled Trial”. Survey Research Methods 16, no. 2 (August 10, 2022): 165-206. Accessed October 1, 2022. https://ojs.ub.uni-konstanz.de/srm/article/view/7651.