Sutter, Matthias Max Planck Institute for Research on Collective Goods, Max Planck Society;
http://dx.doi.org/10.1007/s40881-015-0016-0 (Any fulltext)
Angerer, S., Lergetporer, P., Glätzle-Rützler, D., & Sutter, M. (2015). How to measure time preferences in children: a comparison of two methods. Journal of the Economic Science Association, 1(2), 158-169.