Salvatore Caporaso Michele Zito Nicola Galesi A predicative and decidable characterization of the polynomial classes of languages. 83-99 2001 250 Theor. Comput. Sci. 1-2 db/journals/tcs/tcs250.html#CaporasoZG01 http://dx.doi.org/10.1016/S0304-3975(99)00116-4