Alberto Bertoni Carlo Mereghetti Giovanni Pighizzini On Languages Accepted with Simultaneous Complexity Bounds and Their Ranking Problem. 245-255 1994 conf/mfcs/1994 MFCS db/conf/mfcs/mfcs94.html#BertoniMP94 http://dx.doi.org/10.1007/3-540-58338-6_71