P. Bouyer, A. Petit, and D. Thérien, An algebraic approach to data languages and timed languages, Information and Computation, vol.182, issue.2, pp.137-162, 2003.
DOI : 10.1016/S0890-5401(03)00038-5

URL : http://doi.org/10.1016/s0890-5401(03)00038-5

M. Boja´nczykboja´nczyk, C. David, A. Muscholl, T. Schwentick, and L. Segoufin, Two-Variable Logic on Data Trees and XML Reasoning

P. De-groote, B. Guillaume, and S. Salvati, Vector addition tree automata, Proceedings of the 19th Annual IEEE Symposium on Logic in Computer Science, 2004., pp.64-73, 2004.
DOI : 10.1109/LICS.2004.1319601

S. Demri, R. Lazic, and D. Nowak, On the Freeze Quantifier in Constraint LTL: Decidability and Complexity, TIME'05, 2005.

J. Esparza and M. Nielsen, Decidability Issues for Petri Nets -a survey, Elektronische Informationsverarbeitung und Kybernetik, vol.30, issue.3, pp.143-160, 1994.

K. Etessami, M. Y. Vardi, and T. Wilke, First-Order Logic with Two Variables and Unary Temporal Logic, Information and Computation, vol.179, issue.2, pp.279-295, 2002.
DOI : 10.1006/inco.2001.2953

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.16.6178

J. L. Gischer, Shuffle languages, Petri nets, and context-sensitive grammars, Communications of the ACM, vol.24, issue.9, pp.597-605, 1981.
DOI : 10.1145/358746.358767

E. Grädel and M. Otto, On logics with two variables, Theoretical Computer Science, vol.224, issue.1-2, pp.73-113, 1999.
DOI : 10.1016/S0304-3975(98)00308-9

M. Kaminski and N. Francez, Finite-memory automata, Theoretical Computer Science, vol.134, issue.2, pp.329-363, 1994.
DOI : 10.1016/0304-3975(94)90242-9

URL : http://doi.org/10.1016/0304-3975(94)90242-9

E. Kiero´nskikiero´nski and M. Otto, Small Substructures and Decidability Issues for First-Order Logic with Two Variables, 2005.

S. R. Kosaraju, Decidability of reachability in vector addition systems, STOC'84, pp.267-281, 1984.

R. J. Lipton, The reachability problem requires exponential space, Dep. of Comp.Sci., Research report, vol.62, 1976.

M. Marx, First Order Paths in Ordered Trees, ICDT'05, 2005.
DOI : 10.1007/978-3-540-30570-5_8

E. Mayr, An Algorithm for the General Petri Net Reachability Problem, SIAM Journal on Computing, vol.13, issue.3, pp.441-459, 1984.
DOI : 10.1137/0213029

M. Mortimer, On languages with two variables. Zeitschr. f. math. Logik u. Grundlagen d, Math, vol.21, pp.135-140, 1975.

F. Neven, . Th, V. Schwentick, and . Vianu, Finite state machines for strings over infinite alphabets, ACM Transactions on Computational Logic, vol.5, issue.3, pp.403-435, 2004.
DOI : 10.1145/1013560.1013562

. Th, D. Schwentick, H. Thérien, and . Vollmer, Partially- Ordered Two-Way Automata: A New Characterization of DA, Developments in Language Theory (DLT'01), pp.239-250, 2001.

Y. Shemesh and N. Francez, Finite-State Unification Automata and Relational Languages In Inf, Comput, vol.114, issue.2, pp.192-213, 1994.

D. Thérien, . Th, and . Wilke, Over words, two variables are as powerful as one quantifier alternation, Proceedings of the thirtieth annual ACM symposium on Theory of computing , STOC '98, pp.234-240, 1998.
DOI : 10.1145/276698.276749