Pairat Thorncharoensri Willy Susilo Yi Mu Universal Designated Verifier Signatures with Threshold-Signers. 89-109 2009 IWSEC http://dx.doi.org/10.1007/978-3-642-04846-3_7 conf/iwsec/2009 db/conf/iwsec/iwsec2009.html#ThorncharoensriSM09