Tullio Ceccherini-Silberstein Antonio Machi Fabio Scarabotti On the entropy of regular languages. 93-102 2003 307 Theor. Comput. Sci. 1 http://dx.doi.org/10.1016/S0304-3975(03)00094-X db/journals/tcs/tcs307.html#Ceccherini-SilbersteinMS03