Marcella Anselmo Dora Giammarresi Maria Madonia From Determinism to Non-determinism in Recognizable Two-Dimensional Languages. 36-47 2007 conf/dlt/2007 Developments in Language Theory http://dx.doi.org/10.1007/978-3-540-73208-2_7 db/conf/dlt/dlt2007.html#AnselmoGM07