Brookins, Philip Max Planck Institute for Research on Collective Goods, Max Planck Society;
https://doi.org/10.1016/j.geb.2017.07.008 (Any fulltext)
Boosey, L., Brookins, P., & Ryvkin, D. (2017). Contests with group size uncertainty: Experimental evidence. Games and Economic Behavior, 105, 212-229.