1. Realization of events in nerve sets and finite automata;Kleene,1956
2. IEEE, New York, NY, USA, IEEE Std 1003.1-2001 Standard for Information Technology—Portable Operating System Interface (POSIX) Base Definitions, Issue 6 (2001).
3. H. Thompson, D. Beech, M. Maloney, N. Mendelsohn (Eds.), XML Schema Part 1: Structures, W3C Recommendation, 2001. Available from:
4. Programming Perl;Wall,1991
5. P. Hazel, Perl Compatible Regular Expressions, University of Cambridge. Available from: (2003).