Michal Chytil Vojtech Jákl Serial Composition of 2-Way Finite-State Transducers and Simple Programs on Strings. 135-147 1977 conf/icalp/1977 ICALP db/conf/icalp/icalp77.html#ChytilJ77 http://dx.doi.org/10.1007/3-540-08342-1_11