Narad Rampersad Nicolae Santean Jeffrey Shallit Bala Ravikumar State complexity of unique rational operations. 2431-2441 2009 410 Theor. Comput. Sci. 24-25 http://dx.doi.org/10.1016/j.tcs.2009.02.035 db/journals/tcs/tcs410.html#RampersadSSR09