Hongzhen Du Qiaoyan Wen Shanshan Zhang A Provably-Secure Outsourced Revocable Certificateless Signature Scheme Without Bilinear Pairings. 73846-73855 2018 6 IEEE Access https://doi.org/10.1109/ACCESS.2018.2880875 db/journals/access/access6.html#DuWZ18