Jun Iichi Fujii Ritsuo Nakamoto Kenjiro Yanagi Concavity of the Auxiliary Function Appearing in Quantum Reliability Function. 3310-3313 2006 52 IEEE Transactions on Information Theory 7 http://doi.ieeecomputersociety.org/10.1109/TIT.2006.876248 db/journals/tit/tit52.html#FujiiNY06