Frederik Armknecht Alberto N. Escalante Hans Löhr Mark Manulis Ahmad-Reza Sadeghi Secure Multi-Coupons for Federated Environments: Privacy-Preserving and Customer-Friendly. 29-44 2008 ISPEC http://dx.doi.org/10.1007/978-3-540-79104-1_3 conf/ispec/2008 db/conf/ispec/ispec2008.html#ArmknechtELMS08