An Algebraic View of the Böhm-Out Technique.

Adolfo Piperno An Algebraic View of the Böhm-Out Technique. 233-246 1999 212 Theor. Comput. Sci. 1-2 db/journals/tcs/tcs212.html#Piperno99 http://dx.doi.org/10.1016/S0304-3975(98)00142-X