@article{DBLP:journals/ijprai/OkazakiIIW01,
author = {Tokio Okazaki and
Katsushi Inoue and
Akira Ito and
Yue Wang},
title = {Closure Property of Space-Bounded Two-Dimensional Alternating
Turing Machines, Pushdown Automata, and Counter Automata},
journal = {IJPRAI},
volume = {15},
number = {7},
year = {2001},
pages = {1143-1165},
ee = {http://dx.doi.org/10.1142/S0218001401001398},
bibsource = {DBLP, http://dblp.uni-trier.de}
}