Christian Choffrut Serge Grigorieff Separability of rational relations in A* × N<sup><i>m</i></sup> by recognizable relations is decidable. 27-32 2006 99 Inf. Process. Lett. 1 http://dx.doi.org/10.1016/j.ipl.2005.09.018 db/journals/ipl/ipl99.html#ChoffrutG06