Hiroki Morizumi Jun Tarui Linear-size log-depth negation-limited inverter for k-tonic binary sequences. 1054-1060 2009 410 Theor. Comput. Sci. 11 http://dx.doi.org/10.1016/j.tcs.2008.10.030 db/journals/tcs/tcs410.html#MorizumiT09