Satoru Miyamoto Shunsuke Inenaga Masayuki Takeda Ayumi Shinohara Ternary directed acyclic word graphs. 97-111 2004 328 Theor. Comput. Sci. 1-2 http://dx.doi.org/10.1016/j.tcs.2004.07.008 db/journals/tcs/tcs328.html#MiyamotoITS04