Jeremy Clark Urs Hengartner Kate Larson Not-So Hidden Information: Optimal Contracts for Undue Influence in E2E Voting Systems. 1-17 2009 VOTE-ID http://dx.doi.org/10.1007/978-3-642-04135-8_1 conf/voteid/2009 db/conf/voteid/voteid2009.html#ClarkHL09